Alt-Tab and Workspace Switcher shortcuts aren't working on Xubuntu 21.10

Solution 1:

For me (and many other people) Alt-Tab somehow gets disabled when using Thunderbird and Wayland together, seemingly after one sends a first message with Thunderbird. It's probably something about the "sending message" window not getting terminated correctly. Anyway, see bug 1932328, but the comment 18 fix, putting Thunderbird into XWayland mode, which worked for me, seems to be a fix for many other users.

Another workaround can be to go to keyboard shortcuts and swap Alt-tab and Alt-esc. The latter is "direct window switching" and is similar but different to alt-tab switching. More visually distracting but same functionality.