For anyone curious, LV2 support is in fact enabled when built from the package in the PR, but LV2 plugin paths are not configurable from the GUI. For plugins to show up, the LV2_PATH environment variable needs to be set. In my case using home manager, it's something like /etc/profiles/per-user/username/lib/lv2:$LV2_PATH. Plugins are usable, and their parameters are exposed in score's inspector panel, but launching any plugin's custom UI currently results in error:

suil error: Unable to wrap UI type <http://lv2plug.in/ns/extensions/ui#X11UI> as type <http://lv2plug.in/ns/extensions/ui#Qt5UI>

Score's lead dev wondered if this an issue between suil and Nix, noting that the error indicates that suil can't find /usr/lib/suil-0/libsuil_x11_in_qt5.so. Other programs in nixpkgs that depend on suil (e.g. Ardour) seem to have no trouble displaying plugin UIs, however. There's also nothing special in the packages wrt suil; suil is simply specified as a build input.

Any thoughts?

For anyone curious, LV2 support is in fact enabled when built from the package in the PR, but LV2 plugin paths are not configurable from the GUI. Depending on your system configuration, the LV2_PATH environment variable may need to be set for plugins to show up. In my case using home manager, it's something like /etc/profiles/per-user/username/lib/lv2:$LV2_PATH.

Plugins are usable, and their parameters are exposed in score's inspector panel, but launching any plugin's custom UI currently results in error:

suil error: Unable to wrap UI type <http://lv2plug.in/ns/extensions/ui#X11UI> as type <http://lv2plug.in/ns/extensions/ui#Qt5UI>

Score's lead dev wondered if this an issue between suil and Nix, noting that the error indicates that suil can't find /usr/lib/suil-0/libsuil_x11_in_qt5.so. Other programs in nixpkgs that depend on suil (e.g. Ardour) seem to have no trouble displaying plugin UIs, however. There's also nothing special in the packages wrt suil; suil is simply specified as a build input.

Any thoughts?

Thanks @yuu :) The so file is actually part of suil itself. The following cmakeFlags are also included in the package in the PR:

    "-DSuil_INCLUDE_DIR=${suil}/include/suil-0"
    "-DSuil_LIBRARY=${suil}/lib/libsuil-0.so"

This all led me to believe it was an implementation bug of some kind, but I finally realized that the suil package was for Qt 4, while score was being built against Qt 5. I simply replaced it with suil-qt5 and it worked as expected.

Thanks yuu :) The so file is actually part of suil itself. The following cmakeFlags are also included in the package in the PR:

    "-DSuil_INCLUDE_DIR=${suil}/include/suil-0"
    "-DSuil_LIBRARY=${suil}/lib/libsuil-0.so"

This all led me to believe it was an implementation bug of some kind, but I finally realized that the suil package was for Qt 4, while score was being built against Qt 5. I simply replaced it with suil-qt5 and it worked as expected.