Hi!,

> Hmmmm - - - - I like that - - - - non-compliant - - - - who decided that?

> No logical reason - - - - but there is something called choice - - - yes?
Yes we know systemd kills that thing..

The good news is that you can still use Devuan with usrmerge done and keep
/usr separate; the bad news is that you need to do an extra configuration.

You need to build a custom initramfs for your kernel that takes care of mounting
root AND /usr for you; I never did this but it doesn't look like
rocket science, it just
shell scripting and learing how to customize your initramfs.

Few links that may help:

https://wiki.gentoo.org/wiki/Custom_Initramfs

https://forums.gentoo.org/viewtopic.php?t=912716

Good Luck :)
Lorenzo