It wasn't mentioned in the list, but I like Photoview; it uses your existing file structure (rather than its own structure or a database), works with read-only access, accepts external syncing like Syncthing, and can handle multiple users. Not sure how it compares on features, but I just wanted something basic anyways, so I'm happy with it.

We need a mobile app? Believe it or not, JavaScript, right away. We have the best/worst software in the world because of Javascript.

At least they (hopefully) won't be getting even worse?

I use VSCode and SourceGit. SourceGit is similar to Fork (which I've used before), but it's FOSS and cross-platform (Windows/macOS/Linux).

The best kind of hoard.