Share if you find anything. The only other solutions I've found so far are:
Apple Photos - requires having Apple devices
Plex - meets neither the 'local' nor 'open source' requirement as it sends your photos to some other random cloud provider to scan
If you can find anything, or if anyone else does know, please do share!
Your photos and videos remain on hardware that you own (or rent). It's designed to scale to millions of photos and videos on limited hardware (I run it for my family on a raspberry pi with a big external hard drive that sits next to my router). The browsing experience is fun, both on a 4k display and on my iPhone SE
The only cloud service I run is my licensing storefront, and delegate error reporting to Sentry, which you can opt out of.
Disclaimer: I'm the founder and developer.