[Magisk] return.of.octobot:
Sure thing, I posted some a few posts back but I've just taken another set after running through the process again to try and get the outputs as concise and relevant as possible. I'm uploading two zips each contain a Magisk Log and raw logcat data.

The first set are logs I pulled after the installation process just for the sake of being thorough, but what you'll likely be more interested in are the error logs which I pulled after rebooting and trying to run V4A.

The interesting bit from the error logcat seems to be right here:

Activity launch hint handled
02-15 22:15:14.529 2727 2727 I ViPER4Android: Jni library status = false
02-15 22:15:14.536 2727 4840 D NetworkSecurityConfig: No Network Security Config specified, using platform default
02-15 22:15:14.539 2727 2727 I ViPER4Android: Starting service, reason = ViPER4Android::onCreate
02-15 22:15:14.541 2727 4845 I ViPER4Android: Init environment
02-15 22:15:14.544 2727 4845 I ViPER4Android: Now checking for external storage writable, file = /storage/emulated/0/v4a_test_file
02-15 22:15:14.545 2727 4845 I ViPER4Android: FileNotFoundException, msg = /storage/emulated/0/v4a_test_file (Permission denied)
02-15 22:15:14.545 2727 4845 I ViPER4Android: Really terrible thing, external storage detection failed. V4A may malfunction
02-15 22:15:14.545 2727 4845 I ViPER4Android: Check driver
02-15 22:15:14.551 2727 4845 I ViPER4Android: Found 15 effects
02-15 22:15:14.551 2727 4845 I ViPER4Android: [1], Volume listener for notification, Qualcomm Technologies Inc
02-15 22:15:14.551 2727 4845 I ViPER4Android: [2], Volume listener for voice call, Qualcomm Technologies Inc
02-15 22:15:14.551 2727 4845 I ViPER4Android: [3], Volume listener for alarm, Qualcomm Technologies Inc
02-15 22:15:14.551 2727 4845 I ViPER4Android: [4], Volume listener for ring, Qualcomm Technologies Inc
02-15 22:15:14.551 2727 4845 I ViPER4Android: [5], Visualizer, The Android Open Source Project
02-15 22:15:14.551 2727 4845 I ViPER4Android: [6], Insert Preset Reverb, NXP Software Ltd.
02-15 22:15:14.551 2727 4845 I ViPER4Android: [7], Auxiliary Preset Reverb, NXP Software Ltd.
02-15 22:15:14.551 2727 4845 I ViPER4Android: [8], Insert Environmental Reverb, NXP Software Ltd.
02-15 22:15:14.551 2727 4845 I ViPER4Android: [9], Auxiliary Environmental Reverb, NXP Software Ltd.
02-15 22:15:14.551 2727 4845 I ViPER4Android: [10], Equalizer, NXP Software Ltd.
02-15 22:15:14.551 2727 4845 I ViPER4Android: [11], Virtualizer, NXP Software Ltd.
02-15 22:15:14.551 2727 4845 I ViPER4Android: [12], Dynamic Bass Boost, NXP Software Ltd.
02-15 22:15:14.551 2727 4845 I ViPER4Android: [13], Loudness Enhancer, The Android Open Source Project
02-15 22:15:14.551 2727 4845 I ViPER4Android: [14], Multichannel Downmix To Stereo, The Android Open Source Project
02-15 22:15:14.551 2727 4845 I ViPER4Android: [15], Volume, NXP Software Ltd.
02-15 22:15:14.551 2727 4845 I ViPER4Android: ViPER4Android engine not found
02-15 22:15:14.551 2727 4845 I ViPER4Android: Android audio effect engine reports the v4a driver is not usable

Particularly,

02-15 22:15:14.545 2727 4845 I ViPER4Android: FileNotFoundException, msg = /storage/emulated/0/v4a_test_file (Permission denied)
02-15 22:15:14.545 2727 4845 I ViPER4Android: Really terrible thing, external storage detection failed. V4A may malfunction

02-15 22:15:14.551 2727 4845 I ViPER4Android: ViPER4Android engine not found
02-15 22:15:14.551 2727 4845 I ViPER4Android: Android audio effect engine reports the v4a driver is not usable

The app has indeed been granted storage permissions, which is what made me wonder if this might be an issue with device encryption but I can't really say. I'd be grateful to have you take a look at the big picture within the context of everything else going on. Almost hoping this is going to trigger some 3T/OOS flashbacks.