Tor-browser fails to start - wayland problem

For both versions tor-browser-linux64-12.5a4_ALL as well as tor-browser-linux64-12.0.4_ALL.tar.xz
I get

Blockquote./start-tor-browser.desktop --verbose
Launching ‘./Browser/start-tor-browser --detach --verbose’…
XPCOMGlueLoad error for file /home/jarausch/bin/tor-browser/Browser/
/home/jarausch/bin/tor-browser/Browser/ undefined symbol: gdk_wayland_display_get_wl_compositor
Couldn’t load XPCOM.

I am running a Gentoo Linux system (nearly bleeding edge).

Furthermore I have compiled Index of /torbrowser/12.0.4 myself,
but when I start torbrowser I get
Something Went Wrong!

Tor is not working in this browser.

I would regard myself a quite experienced Linux user, but I am completely new to tor.
Any help is very much appreciated