[Solved] Synthv1 - Ubuntu Studio - installation problem & can't find plugin

please avoid doing that--using alien to convert a rpm into a deb--you'll probably end up with binaries placed on locations that a debian/ubuntu system will never find them (/usr/lib64 instead of /usr/lib, is the most notorious).

i'm sure you'll get way better results if you get it from my Applications PPA's -- see the repositories or go ahead directly to https://launchpad.net/~rncbc ...

for instance, if you are on UbuntuStudio 20.04 LTS (focal fossa), you'll be good with the following:

sudo add-apt-repository ppa:rncbc/apps-focal
sudo apt-get update

then, to install the synthv1 LV2 plugin:

sudo apt-get install synthv1-lv2

hth.
cheers