Just installed Ardour 8.0-rc3 (to /opt directory), and Ardour can’t find avl-drums (lv2) and calf plugins.
Although they are listed in Plugin manager. (Status OK)
I can confirm the problem.
Quick test with 2 calf plugin (phaser, vintage delay).
After a rescan, they are both ok for the plugin manager but they cannot be loaded.
openSUSE TW
UPDATE: avl-drums OK here.
For calf could be related to GTK ?!? Not sure, no issue with eq10q
Plasma. You should resolv your issues if you build Ardour from source (or a package builded for your distro). I have the subscription but I use Ardour builded for openSUSE that for me works better.
The problem exists due to how some distros build the plugins at hand.
Those distros force you to also build the DAW on the same distro where you want to run the plugins. And then there may still be conflicts when loading different plugins.
It is the main reason why pro-audio distros like KXStudio, AVLinux, UbunutuStudio, etc, still exist.
The issue not just affects official Ardour binaries, other DAWs (Reaper, Studio One, Bitwig) have the same issue, and you cannot build them to work around the problem.
Let’s hope the remaining distros will finally make plugins self-contained, and not depend on external resources, like they ought to be and already are on all other platforms.