@martin3141 You can actually do komi betting from the site I created from the Semi-random starting position discussion.
https://runarberg.github.io/random-go-stone-placements/
After you generate a starting position you can copy the URL (which includes the randomly generated placements) and share it with your opponent. You can then do the komi betting, adjust the komi accordingly, download the SGF, upload it to your SGF library, and challenge your opponent.
I admit it is not the most intuitive UX, so I created this issue