I have made some of my suggestions here:
There are a few issues I see with XDA that need quick attention: 1. Posting a new thread Ideally, the 'Post Thread' button should be available universally, and user must choose the appropriate forum (and sub-forum) before the button gets...
I don't agree with your request (2)
"In this regard, it would be nice to have a forum for each version of Android, and then a sub-forum per brand. An issue with a particular version of Android will affect all devices, especially those that are from the same brand. "
IMO, and by my experience, a particular device was originally released with the one version of Android (like A11).and it later receives two or more major upgrades, like A12 and A13
But certain topics like its hardware characteristics and potential issues with (like problems with a fingerprint, problem with the virtual proximity sensor, etc) remain common and some workaround that was posted for an earlier version of ROM may still apply.
Hence they are not related to Android version or brand, but really per device
Then, there are also questions and discussions about the 'best ROM' that generally do not limit to the particular Android version
Etc. Also, guides about unlocking Bootloader, rooting, using and installing a particular custom Recovery might be common
On the other side ok - there are also issues that are common but not only or not that much for the particular Android version but to the vendor's modifications like MIUI versions for Xiaomi phones
Besides, how would you reorganize existing threads where the posts are mixed, related to the same device but different versions of Android (MIUI in the case of Xiaomi phones)
My two cents