Unfortunately I had to reinstall my system (ZorinOS → Ubuntu).
I simply took many plugins from the backup of my user folder and copied them to the appropriate locations in the new system, e.g.
~$/.vst
~$/.vst3
Now I’m trying to tell Ardor how to find the plugin directories.
Unfortunately, it is not possible for me to select directories with dots, i.e. “invisible” directories; these are not displayed in Ardor.
I believe ~/.vst3 is a default path, so you shouldn’t have to worry about that.
To display hidden directories in the “Linux VST2 Path” search window you right-click in the file browser and select “Show hidden files”
~/.vst3 is a default (and mandatory as per the specs, IIRC) path for VST3 plugins. From libs/ardour/plugin_manager.cc : vst3_discover_from_path (“~/.vst3:/usr/local/lib/vst3:/usr/lib/vst3”
VST2 plugins don’t have mandatory locations so you may have to manually specify their location, unless they happen to already be in one of Ardour’s default ones.