thank you man, this is very helpful,If you can enter inside your recovery it's very easy.
You need to go to advanced options --> File manager --> data --> adbm
In this folder you can find yours old magisk module.
Due to encryption it is impossible recognize specific module, and for this reasons you need delete all.
After this you return back to recovery home and flash again your magisk (I used 19.4 canary) .
After this the boot will work without problems .
Inviato dal mio MI 9 utilizzando Tapatalk
it's working for me.