Typo3 DeepL 'No system languages found.' - typo3

Question

I've been working on making my Typo3 11.5 powered site multi-language. To translate the bulk of my content elements I want to use DeepL via https://github.com/web-vision/wv_deepltranslate. While the manually translated pages are shown correctly in frontend, there is still some configuration missing as wv_deepltranslate is not working and its settings screen is showing 'No system languages found.'. The Deepl API Key and the Deepl API Url are set, the translate button is appearing when creating a translation, but pressing it only copies the content element in its original language. I have no clue what setting needs to be made to make the extension work and not show 'No system languages found.' anymore.
My relevant Typoscript setup is
config.sys_language_uid = 0
config.language = de
config.locale_all = de_DE
[globalVar = GP:L = 1]
config.sys_language_uid = 0
config.language = en
config.locale_all = en_EN
[global]
[globalVar = GP:L = 0]
config.sys_language_uid = 0
config.language = de
config.locale_all = de_DE
[global]
and the site config says
languages:
-
title: Deutsch
enabled: true
base: /
typo3Language: de
locale: de_DE
iso-639-1: de
navigationTitle: Deutsch
hreflang: de-DE
direction: ''
flag: de
languageId: 0
websiteTitle: ''
-
title: English
enabled: false
base: /en/
typo3Language: default
locale: en_US.UTF-8
iso-639-1: en
websiteTitle: ''
navigationTitle: English
hreflang: en
direction: ''
fallbackType: strict
fallbacks: ''
flag: en-us-gb
languageId: 1
Edit:
Fixed the 'No system languages found.' by creating the corresponding languages in the list menu on the page root.

Answer 1

Try this:
config {
language = de
locale_all = de_DE.UTF-8
linkVars = L(0-1)
sys_language_uid = 0
}
[siteLanguage("locale") == "en_US.UTF-8"]
config {
language = en
locale_all = en_US.UTF-8
sys_language_uid = 1
}
[end]

Answer 2

Many TypoScript properties you're using are not existing anymore in TYPO3 Version 11. They have been removed in favor of the siteconfiguration.
See in the Changelog/10.0/Breaking-87193-DeprecatedFunctionalityRemoved.html.
Also like #Robert included in his answer already the conditions did change and something like [globalVar = GP:L = 1] is not understood by TYPO3 anymore. Details about the new syntax you can find in the TypoScript Reference, including a link to a more general explanation.
According to the documentation I doubt that the settings by TypoScript are required anyway, the configuration is done in a special module.