Both Excalidraw and TLDraw are the two most popular apps of their kind, simplistic whiteboard tools, so I don't think it's that surprising and I don't see any reason why this post should be a "Show HN".

TLDraw: https://www.tldraw.com/

Excalidraw: https://excalidraw.com/

For me, draw.io is still the winner, and especially now that it runs locally also on Linux. As for works in progress, I hope this one succeeds (and would also run locally at some point):

TikzMaker: https://tikzmaker.com/