[thaumasiotes]

https://nonograms-katana.com seems to have quite a few?

I found it by searching for the much more common name "picross".

[RheingoldRiver]

there are a lot of apps yea, should've specified I wanna solve in my browser. I like doing gigantic puzzles (like at least 30x50) and seeing the whole board at once

[Y444]

Picross is somehow ended up being a trademark of Nintendo iirc

[thaumasiotes]

Trademarking a generic term (that is descriptive of your product) has no legal relevance, even if the term is not generic at the time you trademark it.