It works on Arch Linux with KDE but not on Manjaro with i3-wm.
I have it working on my Manjaro i3.
I followed the guide here: Run Plexamp v3.0.0 on Debian 10 which works great and does away with annoying Library folder being created in our home directories.
Once that was done, I added the following to my i3 config:
bindsym $mod+F5 exec /home/USERNAME/.local/Plexamp/Plexamp-3.0.0.AppImage --no-sandbox
After that it launches fine.
