The version included for this plugin is lagging. The latest stable version for this plugin was 1.1.5. Still, the included version is 1.1.2, and likely the reason why the snap package (which uses your OBS build, but this is Canonical's responsibility) doesn't have this plugin working.

Version 1.1.4 fixed issues for obs 28 and later, which is probably the reason why it is not working, as you can see by the changelog for this version https://github.com/dimtpap/obs-pipewire-audio-capture/releases/tag/1.1.4