Deleting app built using meson

i built this app g4music (https://github.com/neithern/g4music) from source to try some feature (https://github.com/neithern/g4music/issues/78).
now this feature is added in the flatpak version, but i am not able to delete the app

Did you build it using the AUR versions (which also use meson)? If so, uninstalling it should be trivial.

yay -R g4music

If you built it without the AUR or makepkg system, then yes, uninstalling it will likely be a more difficult, manual process.