That's what I thought... was pretty confused. Thanks for the advice, I gave up and factory reset to victory anyway.If you can boot without Magisk and it still does it, it's not caused by this mod. Without Magisk it can't replace any files and Xposed won't work, so the module can't do anything at all.
EDIT: Yeah nope, just did the same thing (after a factory reset) and the step that stops it booting properly is installing the magisk module built in the Ambient app. Realised immediately after I hit reboot that I didn't read the instructions properly - I installed the Ambient magisk module but didn't activate the module in LSPosed, rebooted and black screen.
Though the first time I did it I think I activated the LSPosed module first and that allowed the sound model test to pass after a reboot. After I then installed the magisk module and rebooted I was to booting to a black screen.
As before, tried uninstalling Magisk via twrp (bluspark) and get the same result when restarting.