@nliadm, I found a solution for Fedora on another forum.
I installed compat-openssl10
And running Plexamp, providing a different openssl version than the one used by default:
LD_PRELOAD=/usr/lib64/libcrypto.so.1.0.2o ./Plexamp-3.0.1.AppImage
Seems a common issue with appimage apparently.
