@topjohnwu has left xda due to some reasons.
but before that, he also fixed the bootloop problem.
if you already in the version 19.3, guided by @redymedan, update to new v20.4 by the beta channel...
it works in ata6 build for me, but i can't risk my data again to test on android q.
[update 2] hey folks, after a day testing and stuff, even mess up my sd card with more than 15gb data in it (rip my "homework n stuff"), i had decided that stay in android 9 would be better. Magisk v20.4 COULD works in android 10, but can't do initial setup thingy, so you can't install modules., try to delete MM data and it won't work, conflict with OneDrive maybe.
backup your data, unlock the bootloader and unlock OEM.
open your MM, choose beta channel and refresh, you'll see v20.4 (20400)
copy AP files ( ata6 recommend), to your phone.
select "patch a file", choose the AP files and let the MM do it jobs.
after MM done patching, connect your phone with PC.
open File Explorer, accept permission, copy magisk_patched.tar to your pc.
to Odin, UNTICK THE "AUTO REBOOT" and KEEP "F.RESET TIME"
choose bl file for bl
magisk_patched.tar for ap
cp for cp
and note this: if you choose csc file in csc, you will mess up. your phone will be shrink from 64gb to 16gb.
home_csc for csc.
click start and wait...
after 2 minutes or less, odin will say "PASS".
next step will be hard, buy some coffee for
concentrate in pressing buttons (lol)
press volume down and power for more 7s, when screen blank, use 50% of your mana and press both volume up and power.
when samsung text appear, hold till it pass the bootloader warning, after that, only keep the volume up.
after a few secs, you will see text "erasing" and the screen will eventually blank again.
continue the process, do as above, and keep the volume up button to enter recovery mode.
wipe all data&factory reset.
choose the "reboot system now", when the screen blank, immediately hold both power up and power until it passes the bootloader warning.
the first time it boot, it won't boot to os but instead it will reboot again, dont panic, just stay at natural.
do setup, PLEASE NOTE THAT DO NOT CONNECT WIFI IN SETUP OR ELSE YOU WILL GET IN BOOTLOOP.
after setup, you can connect to wifi.
go to MM to do initial setup, and done.
feel free to restore your data, install modules, block ads,...