Just flash with twrp than install Magisk manager app. İf you have any bootloop orcrash just flash with uninstaller..
Magisk v 19.1
Magisk Manager v7.1.2
Magisk Uninstaller
Hi i already do it Like you only differences is I just install busybox inside magisk and after that host file is working well. İt's working after restart aswell.. let's try :)