Aspects that I think are important include the community of maintainers in addition to the current state of functionality
Maintenance has been zero, aside from when I want to add functionality.
My only feature gripe is that gPhotos has a wonderful "archive photos" feature to delete local copies of media already uploaded. You can still see uploaded photos (thumbnails stay local) and any interaction with them stays "as if local", there's just a delay while it downloads a temporary copy. I wish nextcloud had this capability.
Photoprism is also somewhat unique in that it uses Darktable to process RAW photos, so if you use Darktable and have it write XMP sidecars, Photoprism will be able to process the adjustments.
For more curated collections, I prefer Piwigo, as it has a mode where it converts a directory tree into an album tree. It also has pretty good sharing features. Photoprism on the other hand is horrible for pre-curated photos.
[1]: https://piwigo.org/
So far the setup was pretty easy on my VM but I kicked the tires with their VM image first. And so far the Android app is doing mostly OK. There is a lot to get into. And extensions out the wazoo.
I've not had to work with any community (yet) cause so far, it's just work - or there is some config I need to tweak (docs are great!)
With their VM and docker images tho, super easy to kick tires.
So if we are talking a just about a few hundred MB of photos, you are probably fine, but for anything larger I would recommend to consider one of the more specialized projects.
I haven't used PhotoPrism, but wanted to toss it out there as an alternative.
This builds the thumbnails in the background. I think it used to get triggered on upload but says it needs a cronjob now. Works OK on a folder of 40GB of photos.
What I still find irritating about photos in nextcloud is I keep mine in high resolution but nextcloud won't downscale them to fit the viewing device screen, so I use 20mb a photo with all the UX impairment one might imagine when actually a few kB would do. It'd be nice if it cached light, fullscreen versions and offered a "view in full resolution" button.
More info: https://docs.photoprism.org/user-guide/settings/advanced/#im...
Yes, I have no idea what they don't do this. This makes the gallery barely usable.