That's error -2Hey peeps. If you ever have the Error 20 while doing a manual upgrade using the internal updater. Switch the time zone to manual and choose Shangai. Once the update is done, go back to the system settings to sitch back to the network-provided time+time zone.
Error 20 happens when the phone's images are not stock (mainly boot.img)
So either stock images still have to be reapplied with magisk -> uninstall or the images restored by magisk were not stock.