This appears to be fixed in thunderbird 1:102.6.0-1 which includes the following in /etc/apparmor.d/usr.bin.thunderbird:
# Imported from the opencl abstraction, which we cannot include
# due to conflicting "x"
@{sys}/devices/pci[0-9]*/**/{class,config,resource,revision} r,
I have not checked which version first contained these lines.
I'm not closing this bug report yet because bullseye is still affected.
