I tried just yesterday with latest firefox and fedora, screen sharing didn't work out of the box. Only screen sharing by creating a virtual display worked, not sharing the current screen nor tab.
I have one thats purveying over apparently linux, mac, chrome, firefox... when you screenshare on multiple monitors (or workspaces) the screen stops updating.
Screen sharing? Hold on, those extra-advanced features could wait. Microsoft should focus first on message delivery (notifications may be delayed for hours), showing media in chats (picture and videos fail to show most of the time) and just opening conversations correctly from notifications (message from a person opens a group chat, sometimes that forks a conversation, leading to loss of history). That’s the very basics for every messaging app, and even those don’t work properly.
(This is about official Windows and iOS Teams apps. I haven’t yet tried any GNU/Linux options.)
If we're listing Team's idiosyncrasies, when you're chatting with exactly one person in a group chat after all the others have left, their name becomes "just me". You won't ever see their real name again.
Most annoying bug I experience is occasionally all messages I send not being delivered silently. You only realize it after a long while when no one seems to react to anything you say. Open in another device and you can't see your own messages. They are not delayed they just never get delivered. Such an unreliable tool being used in a professional environment.
Pretty sure any screen sharing from a browser app would use the browsers screen capture api, which should just use your desktops screen sharing portal if on Wayland. Maybe make sure you have the desktop portal for your DE installed.
That's not the issue. If other apps can screenshare but teams can't that's a teams problem not a DE problem.
Also switching user agent to chrome fixes the issue (but creates a different issue where you can't join calls sometimes)