Eclipse Missing javax.xml.bind With Java 11 at Launch of Eclipse - eclipse

Question

Maybe I should write as the first line: this isn't about writing code and needing JAXB as some form of dependency
I keep having problems when launching Eclipse 2021-03 and 2021-06 with Java 11 as it's missing the JAXB support. Several solutions I could find about this matter actually talk about how to make it work as part of a Java/Maven-project. However, I'm talking about Eclipse here, launching it, not writing code.
Side note: It also occurs while building a project of ours that requires JAXB, which works fine when built with Maven inside Eclipse. So it's an Eclipse-only problem.
This can be reproduced with MoreUnit installed and navigating in the Preferences to MoreUnit > Java > Mock Generation, which leads to this:
java.lang.ClassNotFoundException: An error occurred while automatically activating bundle org.moreunit.mock (932).
at org.eclipse.osgi.internal.hooks.EclipseLazyStarter.postFindLocalClass(EclipseLazyStarter.java:126)
at org.eclipse.osgi.internal.loader.classpath.ClasspathManager.findLocalClass(ClasspathManager.java:572)
at org.eclipse.osgi.internal.loader.ModuleClassLoader.findLocalClass(ModuleClassLoader.java:345)
at org.eclipse.osgi.internal.loader.BundleLoader.findLocalClass(BundleLoader.java:401)
at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:480)
at org.eclipse.osgi.internal.loader.ModuleClassLoader.loadClass(ModuleClassLoader.java:170)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:519)
at org.eclipse.osgi.internal.framework.EquinoxBundle.loadClass(EquinoxBundle.java:622)
at org.eclipse.core.internal.registry.osgi.RegistryStrategyOSGI.createExecutableExtension(RegistryStrategyOSGI.java:196)
at org.eclipse.core.internal.registry.ExtensionRegistry.createExecutableExtension(ExtensionRegistry.java:920)
at org.eclipse.core.internal.registry.ConfigurationElement.createExecutableExtension(ConfigurationElement.java:246)
at org.eclipse.core.internal.registry.ConfigurationElementHandle.createExecutableExtension(ConfigurationElementHandle.java:63)
at org.eclipse.ui.internal.WorkbenchPlugin.lambda$0(WorkbenchPlugin.java:287)
at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:74)
at org.eclipse.ui.internal.WorkbenchPlugin.createExtension(WorkbenchPlugin.java:285)
at org.eclipse.ui.internal.dialogs.WorkbenchPreferenceNode.createPage(WorkbenchPreferenceNode.java:52)
at org.eclipse.jface.preference.PreferenceDialog.createPage(PreferenceDialog.java:1280)
at org.eclipse.ui.internal.dialogs.FilteredPreferenceDialog.createPage(FilteredPreferenceDialog.java:338)
at org.eclipse.jface.preference.PreferenceDialog.showPage(PreferenceDialog.java:1166)
at org.eclipse.ui.internal.dialogs.FilteredPreferenceDialog.showPage(FilteredPreferenceDialog.java:630)
at org.eclipse.jface.preference.PreferenceDialog$5.lambda$0(PreferenceDialog.java:660)
at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:74)
at org.eclipse.jface.preference.PreferenceDialog$5.selectionChanged(PreferenceDialog.java:657)
at org.eclipse.jface.viewers.StructuredViewer$3.run(StructuredViewer.java:823)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:45)
at org.eclipse.jface.util.SafeRunnable.run(SafeRunnable.java:174)
at org.eclipse.jface.viewers.StructuredViewer.firePostSelectionChanged(StructuredViewer.java:820)
at org.eclipse.jface.viewers.StructuredViewer.handlePostSelect(StructuredViewer.java:1193)
at org.eclipse.swt.events.SelectionListener$1.widgetSelected(SelectionListener.java:84)
at org.eclipse.jface.util.OpenStrategy.firePostSelectionEvent(OpenStrategy.java:263)
at org.eclipse.jface.util.OpenStrategy.access$5(OpenStrategy.java:258)
at org.eclipse.jface.util.OpenStrategy$1.lambda$1(OpenStrategy.java:428)
at org.eclipse.swt.widgets.RunnableLock.run(RunnableLock.java:40)
at org.eclipse.swt.widgets.Synchronizer.runAsyncMessages(Synchronizer.java:185)
at org.eclipse.swt.widgets.Display.runAsyncMessages(Display.java:5096)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:4602)
at org.eclipse.jface.window.Window.runEventLoop(Window.java:823)
at org.eclipse.jface.window.Window.open(Window.java:799)
at org.eclipse.ui.internal.OpenPreferencesAction.run(OpenPreferencesAction.java:66)
at org.eclipse.jface.action.Action.runWithEvent(Action.java:474)
at org.eclipse.jface.action.ActionContributionItem.handleWidgetSelection(ActionContributionItem.java:580)
at org.eclipse.jface.action.ActionContributionItem.lambda$4(ActionContributionItem.java:414)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:89)
at org.eclipse.swt.widgets.Display.sendEvent(Display.java:5879)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1427)
at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:5121)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:4599)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$5.run(PartRenderingEngine.java:1157)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:338)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1046)
at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:155)
at org.eclipse.ui.internal.Workbench.lambda$3(Workbench.java:644)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:338)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:551)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:156)
at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:152)
at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:203)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:134)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:104)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:401)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:255)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:78)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:567)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:654)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:591)
at org.eclipse.equinox.launcher.Main.run(Main.java:1462)
at org.eclipse.equinox.launcher.Main.main(Main.java:1435)
Caused by: org.osgi.framework.BundleException: Exception in org.moreunit.mock.MoreUnitMockPlugin.start() of bundle org.moreunit.mock.
at org.eclipse.osgi.internal.framework.BundleContextImpl.startActivator(BundleContextImpl.java:835)
at org.eclipse.osgi.internal.framework.BundleContextImpl.start(BundleContextImpl.java:763)
at org.eclipse.osgi.internal.framework.EquinoxBundle.startWorker0(EquinoxBundle.java:1028)
at org.eclipse.osgi.internal.framework.EquinoxBundle$EquinoxModule.startWorker(EquinoxBundle.java:371)
at org.eclipse.osgi.container.Module.doStart(Module.java:605)
at org.eclipse.osgi.container.Module.start(Module.java:468)
at org.eclipse.osgi.framework.util.SecureAction.start(SecureAction.java:511)
at org.eclipse.osgi.internal.hooks.EclipseLazyStarter.postFindLocalClass(EclipseLazyStarter.java:117)
... 68 more
Caused by: java.lang.NoClassDefFoundError: javax/xml/bind/JAXBException
at org.moreunit.mock.config.MockModule.getXmlTemplateDefinitionReader(MockModule.java:168)
at org.moreunit.mock.config.MockModule.prepare(MockModule.java:81)
at org.moreunit.core.config.Module.start(Module.java:72)
at org.moreunit.mock.MoreUnitMockPlugin.start(MoreUnitMockPlugin.java:24)
at org.eclipse.osgi.internal.framework.BundleContextImpl$2.run(BundleContextImpl.java:814)
at org.eclipse.osgi.internal.framework.BundleContextImpl$2.run(BundleContextImpl.java:1)
at java.base/java.security.AccessController.doPrivileged(AccessController.java:554)
at org.eclipse.osgi.internal.framework.BundleContextImpl.startActivator(BundleContextImpl.java:806)
... 75 more
Caused by: java.lang.ClassNotFoundException: javax.xml.bind.JAXBException cannot be found by org.moreunit.mock_3.2.1
at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:519)
at org.eclipse.osgi.internal.loader.ModuleClassLoader.loadClass(ModuleClassLoader.java:170)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:519)
... 83 more
So pretty much the only information I could find is this comment from 2019 about an older Eclipse-version that could still run with an older Java-version. However, for two versions or so Eclipse has to run with Java 11 minimum. And that's where the troubles start.
Note that I'm a total noob in the JAXB-, OSGI- and bundling area and maybe I didn't understand that a certain answer on the internet may have fixed it for me. What I've tried:
adding -Dorg.osgi.framework.bundle.parent=ext to eclipse.ini doesn't fix it
adding -Dorg.osgi.framework.bundle.parent=app to eclipse.ini doesn't fix it
adding --add-modules java.xml.bind to eclipse.ini doesn't fix it, launching it results in an exit code 1:
[sjngm#sjngm eclipse]$ eclipse -consoleLog
Error occurred during initialization of boot layer
java.lang.module.FindException: Module java.xml.bind not found
Gtk-Message: 22:28:53.909: GtkDialog mapped without a transient parent. This is discouraged.
[sjngm#sjngm eclipse]$ echo $?
1
[sjngm#sjngm eclipse]$
Anything else I can try?