Lemmy seems like the right place to ask this. Personally I’ve really enjoyed Gurgle, which is a FOSS Wordle clone app.
Obsidian for Knowledge base, note taking. https://obsidian.md
Edit: TIL not open source. sorry. They even had a Github and all. I wasn’t paying attention. I have to move now :(
I’ll second Openstreetmap, I use it exclusively. There’s also a set of lightweight versions that are locally hosted, so I use osmap.nl if I want to quickly look at where something is. It also forces the names to the language of the server, so you can use it to improve a second language.
I use an adblocker on my phone called Blokada. It blocks adverts in apps as well as on websites, so I don’t get adverts if I play something like Words With Friends for example. Also blocks adverts on Youtube which is an absolute godsend. Advertising is one of the few things I get irrationally upset about.
I make music using LMMS. It has its limitations but it’s quite versatile if you’re handy with it. This song was made in it for example: https://on.soundcloud.com/dTqgb
I use Betterbird for email on my PC. It’s Spartan in design, which is what I’m into, and you can sign in with multiple addresses. I use K-9 Mail on my phone which has the same advantages.
I use an app called Saisonkalender to look at what veg is in season. Quite niche but it’s handy for ordering ingredients for soup of the day in work.
I have a game on my phone called Lexica which is basically Boggle. It’s good fun.
Yunohost! If you want to get started self-hosting some services, check out Yunohost. It’s super easy to setup and run, active development and community, and just awesome. I found it so much easier than docker-based projects. I used to have it running on an old eeepc netbook, but now I have a dedicated tower server for it.