According to the debian wiki support is not fully guaranteed. Might just be that you ran into any of those issues:

Wayland support is still not finished yet though. Notably, there are issues with the compositor taking down other applications with it when it crashes, changing the global theme sometimes causes a session crash, "Activities" are unimplemented, there are various papercuts with drag-and-drop functionality, and session restoration only works with XWayland windows. A full and more regularly-updated list of Plasma Wayland issues can be found here: https://community.kde.org/Plasma/Wayland_Showstoppers

Can you confirm that it's only the taskbar that freezes? Do any other DE components (e.g. app launcher (shortcut meta + f2 by default)) work or do they freeze/not respond as well?

You could check various logs for errors:

• syslog (/var/log/syslog or dmesg)
• unit files of Plasma components (journalctl -xeu $UNITNAME; e.g. journalctl -xeu sddm.service)