Hey, @unfa, haven't searched much about this, but what have you done now that some LV2 plugins don't show their custom GUI?
I found this affecting some packages of Arch: https://bbs.archlinux.org/viewtopic.php?id=310058
@porru Maybe this link could be helpful: https://github.com/falkTX/lv2-gtk-ui-bridge
I'm using it in Ardour for older projects that use Calf plugins.