I think I waited long enough and went ahead now - even though the distribution of thanks is a little discouraging.

https://coderus.openrepos.net/pm2/pr...lume-warning-2

I've already tested the patch itself for over a week; it does what is desired and seems to have no impact on pulseaudio volumes.
I have installed it through pm3 now (after first undoing the manual patch) and that seems to be working too.

A note for devlopers:
The usage instructions say that .tar.xz is a valid extension, but my Xperia XA2 would not install the patch (even though the archive is intact on my computer).
The phone's journal states "tar: invalid magic" and "tar: short read".
Compressing it as .zip solved that.