I’m not entirely sure that there is really no other official source for local group funding. Please correct me in the comments.
It seems that by now, CEA's community building grants programme is the only source of funding for local group leaders and community builders world-wide. (The EA meta fund distributed some funding to community builders in earlier rounds, although the bulk of the money went to other targets. In the latest round, they referred community builders to the community building grants programme and they plan on continue doing so in the future.)
According to CEA’s org chart, it’s mostly Harri who is responsible for the community building grants. All funding decisions regarding community building are thus probably made by a single person. (Edit: Although Harri is leading the process, there are actually several people involved in making funding decisions. See comments.)
By comparison, e.g. AI safety research has a more diverse funding landscape within EA: OpenPhil (direct grants, PhD fellow programme), BERI, FLI, the longterm future fund, I think MIRI has/had a programme to fund career transitions, there is/was funding for individual researchers publicly announced on the 80000 hours job board, … . Each of these often has several people working on funding decisions.
Additionally, most other top cause areas can get funding from outside of EA (e.g. traditional academic funding sources for academic research) or can be tackled by working at a for-profit. These sources probably don’t exist for community builders.
Of course, community builders can raise funding from individual donors, but that involves significant coordination and vetting costs. I would guess that most funding for community builders does in fact come from CEA’s community building grants.
EA movement building is one of our top cause areas, but all funding decisions are concentrated in literally one person (Edit: Not true, see comments). That seems bad. I would much prefer there to be at least a few grant makers, view different world-views, epistemics, and networks, preferably located at different organisations.
One actionable take-away from this for private funders: In a healthier funding landscape, if you are approached by a community builder that wasn’t able to secure funding through official channels, you might think twice about funding them. After all, they were already vetted by several people at several orgs and found not worth funding. However, in the current funding situation, this intuition would be misguided: literally only one person vetted them.