I updated my branch so the installation also runs on Devuan 2, 3 and 4 (ascii, beowulf and chimaera). The php versions are not changed (ascii+stretch <= php 7.4, the others including also php 8.0).
Important: the installer changes some code in the install folder if needed... not very elegant but at the moment the only way to deal with the changes in the versions...
Still not ok: installing roundcube.
I always use a second SSH login to change the file
as soon as it's downloaded (after entering IP/password and mail address it starts)
Change line 128: add a "-L " after the first %s - so it looks like this:
on my vm I have enough time to do this... then the installation finishes smoothly.
I think it's time to add newer PHP versions to the 6 distributions.
If someone is here doing the job for ubuntu (xenial?, bionic, focal, and maybe already jammy)... pleas go ahead!
Update: now also PHP 8.1 is included in the Debian/Devuan package lists.