Hello, I've started porting Calligraplan to KF6/Qt6. It compiles links and runs (on Linux), but I haven't tested it further.
There are still quite a few warnings; if I have some time, I'll take care of them. If you want to take a look, I've committed it to https://github.com/miko53/calligraplan.git in the port-kf6-qt6 branch.
Regards, Miko