There isn’t a 1:1 FOSS replacement for Notion. I’ve been also looking for one and haven’t found any.

As others have said, Appflowy and Affine are the best options that don’t require self hosting. Appflowy now has a web version too. There’s also SiYuan.

If you’re fine with self hosting there might be a few options mainly for database like functions, some provide a free trial/tier :

1. Undb

2. Teable

3. Docmost

This maybe ?

https://opensourcedesign.net/jobs/

https://discourse.opensourcedesign.net/

If you want a proper journaling app :

Inner Ink

Linked

Rednotebook seems solid

Having markdown means you can use it in a variety of apps but I’m not sure how many have encryption (obsidian and joplin maybe?)

You could also try Trilium Next

I also found Darkwrite. Can export as HTML

I recently found this on github : Muzik-offline

I’m also keepin an eye on this as it has flac support : Wora

There are more on this list : Alternativeto

foobar and musicbee are not open source afaik

Paisa was open source. The developer then removed it I guess. The repo you linked doesn’t host the app. The developer said it’s used for reporting issues. Edit : The repo is private

Cashew is open source GPL licensed. But it uses Google libraries which I guess prevents it from being on f-droid. Last time I used Cashew, the premium features notifications could be ignored and the app could be used completely for free, I’m unsure if that was changed though.

I found another app but it’s not on f-droid, you’ll have to use Obtainium - Monekin