I've been using SimpleX, and I like it a lot. Very polished and reliable. The company is registered in the UK.

I use Shotwell to organize my photos. It can handle creating folders by date automatically, and allows you to rate and tag. It works well for my needs.

Gorgeous.

I've used Yacy for years. It's very customizeable and gives good results, and I like that I can curate, to some degree, what it finds. Biggest drawback is that I don't always feel like starting up a server to do a search.