I'm having these kinds of issues too on Beta 6. Only on M1 devices, Intel based are working fine. USB-C monitor with built in dock, sometimes works, sometimes works but no power delivery. If device rebooted with USB-C monitor connected, then it works - but unplug the cable and replace, and back to no power/accessories. Looking forward to Beta 7.... :)

Release version of Monterey still has this issue! - come on Apple!!