Hey just some notes on how nonprofit fiscal sponsorship stuff works (I have worked in ops for charities for a while now) -- 

• Not sure if the grant acceptance was your only evidence, but the fact that RC was the receiving charity for a grant in 2022 doesn't necessarily mean they are fiscally sponsoring Nonlinear (or were at the time). I can think of a few reasons related to bank set up times, international transactions, etc. that a charity might ask another charity to receive the grant for them, although it is a bit weird. 
• If RC is the fiscal sponsor, it looks like most of RC's fiscal sponsorship projects are Model C. There are a bunch of different fiscal sponsorship models with different implications for the relationship. Model C means they are basically just a pass-through for funds, so Nonlinear would have had to have its own governance board, if one exists. 
• Depending on what exactly Nonlinear is, from a legal perspective, it may not have a board. As far as I can tell, they have no information about their corporate structure on their website; they list several "advisors" but that doesn't seem to be a governance board. If Nonlinear doesn't have a board, that reflects somewhat poorly on the due diligence of RC's regranting, but explains why the employees might not have had anyone to complain to.
• A google search reveals that Spartz Philanthropies had it's nonprofit status revoked by the IRS for failing to file their tax documents for 3 consecutive years. So it seems unlikely that they're doing formal fiscal sponsorship through that group either.