when i open the plugin manager in 8.1, add a vst2path and click add there is only a partial list of folders displayed so i am unable to point ardour to the correct directory with the plugins. manually imputing the path does not work. also right click and show hidden files does nothing. also the defalult path in 8.1 is /app/extentions/… which i can see when i click on file system icon in the add a vst path but when i look through file explorer or terminal i cant find this folder. not sure if this is some sort of virtual folder.
in ardour 6.9 doing the same thing, it shows the entire file structure, drives and folders and works like i would expect. not sure if 8.1 does things differently or if this is a bug in 8.1 both were installed through software manager.
In this case you need to contact the flathub team where you got Ardour from.
Flatpak’s concept to isolate individual apps in a dedicated sandbox is conceptually at odds with loading 3rd party [plugin] binaries (and may also introduce additional overhead). If I understand correctly: the flatpak’ed version of Ardour can only use flatpak’ed packaged plugins (or those in your user’s home/data folder).