Skipping acquire of configured file '.. doesn't support architecture 'arm64' - raspberry-pi

Question

whenever I do sudo apt-get update this output appear
$ sudo apt-get update
Hit:1 http://archive.raspberrypi.org/debian buster InRelease
Hit:2 http://raspbian.raspberrypi.org/raspbian buster InRelease
Reading package lists... Done
N: Skipping acquire of configured file 'main/binary-arm64/Packages' as repository 'http://raspbian.raspberrypi.org/raspbian buster InRelease' doesn't support architecture 'arm64'
N: Skipping acquire of configured file 'contrib/binary-arm64/Packages' as repository 'http://raspbian.raspberrypi.org/raspbian buster InRelease' doesn't support architecture 'arm64'
N: Skipping acquire of configured file 'non-free/binary-arm64/Packages' as repository 'http://raspbian.raspberrypi.org/raspbian buster InRelease' doesn't support architecture 'arm64'
N: Skipping acquire of configured file 'rpi/binary-arm64/Packages' as repository 'http://raspbian.raspberrypi.org/raspbian buster InRelease' doesn't support architecture 'arm64'
and it's so annoying that there are >N: Skipping acquire of configured file line, although these line are not affect the performance, I mean I can still update or upgrade packages or even install packages without problem.
so the question is, how can I remove those >N: Skipping acquire of configures file message

Answer 1

I had the same problem. I fixed it by entering the following command:
sudo dpkg --remove-architecture arm64
I suspect I may have added the arm64 architecture by mistake at some earlier time. The standard 32-bit Raspberry Pi OS (aka Raspbian) does not support 64-bit applications.

Answer 2

Because a repository which defined in your sources.list doesn't support one of your APT::Architectures config options.
Usually, a software developers in their installation's guides writes a common form of repository specification, like a
deb uri suite component1 [component2 component3 ... ]
This is a one-line-style format specification of repository. I assume that your specification looks like:
deb http://raspbian.raspberrypi.org/raspbian buster InRelease,
where http://raspbian.raspberrypi.org/raspbian is a uri, buster is a suite, and InRelease is a component1. The deb uri suite component1 format is the simplest, and it will guarantee that apt-get will work forever with that repository on the most of user's computers. But, there is a little trap: the developers doesn't know in advance which architectures supported on every machine of every user. When a user have architecture, which is not present in repository, he get the Skipping acquire of configured file '.. doesn't support architecture 'arm64' error.
An answer in the man sources.list:
The format for two one-line-style entries using the deb and deb-src types is:
deb [ option1=value1 option2=value2 ] uri suite [component1] [component2] [...]
deb-src [ option1=value1 option2=value2 ] uri suite [component1] [component2] [...]
, and:
Architectures (arch) is an option. If this option isn't set the default is all architectures as defined by the APT::Architectures config option.
It means that architecture arm64 is also set on your machine, and packages with this architecture requested by your package manager when it is calling that repository. All your APT::Architectures you can see in /etc/apt/apt.conf, or executing in the bash:
> apt-config dump | grep -F "APT::Architectures" -
The correct solution of your issue is to use a repository specification with defined Architecture option. If you need the arm, not the arm64, then specification should be:
deb [arch=arm] http://raspbian.raspberrypi.org/raspbian buster InRelease
With this format the apt package manager will request only packages with arm architecture from the repository.