I get the impression that nobody knows, so I did some research.
Apparently, there is a known bug in OGS’ automatic handicap calculation on 9x9 (this might explain why nobody knows). So whatever handicap is calculated now, it is not what OGS intended. So better set it manually (but it makes me wonder how those OGS 9x9 handicap tournaments can work with broken automatic handicap).
I could not find how OGS’ automatic handicap 9x9 should be computed. AFAIK there is no universal standard for this, but the AGA has a standard and there are several variants used in Europe. I picked a few and plotted a comparison chart:
To make that chart, I used 2 x 6.5 komi for a full handicap stone to allow combinations of handicap stones + komi in each curve. The 6.5 komi value is what KataGo considers fair for 9x9 even games. The numbers on the vertical axis correspond to “full” handicap. So 1 handicap means 2 stones with black giving 6.5 komi.
In this chart you can see:
- The AGA is the most generous with handicap: 1 stone per 4 ranks.
- Next is Baarle (NL) youth club system with 1 stone per 6 ranks (it has a staircase shape, because it doesn’t use komi).
- Then comes BGA/Cambridge system with 1 stone per 7 ranks.
- And finally, Nijmegen (NL) is the most cringy with handicap: only 1 stone per 7.5 ranks (but that’s still close to the Cambridge system).