I can confirm this issue. Flashing 1.5 over 1.42 breaks root. Magisk modules such as viper4android and youtube vanced install but fail to appear in launchers. At some point I got error that magisk was not installed and had no root. Restoring boot backup didn't work.; I got stuck at nvidia logo. I finally fixed the magisk root issue by flashing kernel version 1.42 first then booting back to recovery again and flashing magisk 20108 (fresh install of kernel only doesn't fix magisk). Other versions of magisk didn't work. Problem must be with the kernel.@rootfan
Thanks for 1.5 kernel. Seems to work great on Shield 2017 16gb with 8.0.1 dev pie.
Magisk 20108 is the last working one. Latest 20109 don't work anymore. (No root after reboot) It was the same on 1.4. So I don't think it's a fault of your kernel. Hopefully topjohnwu will fix that soon