Hi,
Several steps you could have a try:
1.Go to Microsoft Remote Desktop > preferences > General Tab> uncheck “use system proxy configurations “ and
Also uncheck “Use hardware acceleration ”
This is one suggestion shared in another thread and many users reported that if fixed their issues.
https://learn.microsoft.com/en-us/answers/questions/163352/after-big-sur-was-loaded-on-mac-book-pro-now-the-m.html
2.Please try the beta version which included the newest testing features than the officially released version:
https://install.appcenter.ms/orgs/rdmacios-k2vy/apps/microsoft-remote-desktop-for-mac/distribution_groups/all-users-of-microsoft-remote-desktop-for-mac
3.Please also update the VPN version if used in your remote connection.
Hope this helps and please help to accept as Answer if the response is useful.
Thanks,
Jenny