The Pixel camera app is available from the Play Store, and there are third-party ports of Gcam to other devices that offer extra configuration options. https://www.celsoazevedo.com/files/android/google-camera/

I'd also be interested to know if a Google Camera app installed post-facto to LineageOS is compatible with the remote control & viewfinder of the Pixel Watch.

Well, they are good enough for me, but to be honest, I'm not particularly picky... As said in a parallel post, you can get GCam in APK form (I run LineageOS without GApps) but I hear it's a bit trial&error to find one that works and I haven't bothered.

Loved the photos from my 4a when I had it many years ago.

Videos, on the other hand...