I like Excalidraw too, but in my opinion OurBoard has a different focus.
- Excalidraw is superb if you want to draw something freestyle.
- Ourboard seems to focus more on creating boxes (notes) which you can group and connect. If I understand it correctly, you can even load Github issues into your board.
At the start of the pandemic, I searched for Whiteboards where I could draw things freestyle (installed MS Whiteboard), but over time I noticed, that I used MS Powerpoint most of the time, because it was so much better at handling boxes in collaborative environments. I think OurBoard could be even better at this job.
Miro has an interesting learning curve (at least for me). I absolutely hated it for the first couple dozen times I used it.
Then, there was one meeting where it was particularly effective in running a “sticky note” exercise and my opinion on it flipped that day from around -7 to +3 [on a -10 to +10 scale]. It’s grown slightly on me since then as well; I might be a +5 on it right now.
No signup needed, clean interface, fast load times and an option to self host makes it an excellent product.