If you are reporting specific bugs, crashes, or performance issues, I would post those in the Bug Report forum: https://forum.paradoxplaza.com/forum/index.php?forums/battletech-bug-reports.998/
If you are making suggestions for things that you would like to see changed, I would post it in the Suggestions forum: https://forum.paradoxplaza.com/forum/index.php?forums/battletech-suggestions.997/
Other general feedback can just go in the main forum.
Make sure that you include [Linux Beta] in the thread title for bug reports or suggestions so that it can get noticed by the right people on the dev team.
Thank you for your help!