I forgot to mention your app, I use it on my phone. Pretty fast app.
I was planning to add an issue - when the numbered list reaches 3 digits, it overflows to the next line. This was the reason I went back to Joplin. But I have high hopes for your app :)
Beaver Notes. The android version is in early dev called Beaver pocket. Do note, it does not have folder/notebook feature afaik
SiYuan. You can notes as Markdown files but their sync requires payment (I don’t know much about Siyuan’s pricing). I don’t use this as it has “AI”, it can be disabled but I didn’t need it in the first place.
Joplin and Beaver Notes (soon) support syncing with syncthing and other similar options (Joplin also has it’s own paid cloud sync afaik)
The rest are available on Linux, but if you export the notes, you can use Markor on Android
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 :
Chaski
Lettura