I have installed Tryton 6.0 client via pip3 on a fresh Tumbleweed system and MATE desktop, Python 3.8.8
When attempting to connect to the demo server it crashes with:
ModuleNotFoundError: No module named ‘pygtkcompat’
As this was an issue for Tryton 5.0 (Why does Tryton still needs pygtkcompat library?), I seem to remember that full Python3/GTK3 compatibility was planned for Tryton 5.2?