There is a lot of conjecture in suggestions the Jassim bid is from Qatar. You're right there is no proof. What's more there seems a district change in approach to United, less open, than in other Qatar purchases that cannot be explained with proof. If indeed someone thinks Qatar is purchasing United. There is historical precedence where benefactors have purchased clubs which go largely ignored, old uncle Jack or RA. They're not on the level of the united sale, even after taking into account time variation of money, and there seems plenty of myths, which with a little research e.g. reading annual reports etc can be busted. e.g. QIA owning the majority of QIA which is false, Jassim/HJB being a close relative of the Emir. A prominent comment from some is that HJB had roles in running the country and QIA. He (HBJ) was removed immediately from positions of power in 2013 by the current Emir and hasn't been given power back. I'm not sure how people square the position that Jassim, whose father who was removed from power and never allowed back is currently being backed by the Emir. That is particularly questionable given the size of the family, and the distance from the Emir to Jassim. It is also just as questionable to think QIB might have been set up to buy United, that sure is some far ahead wishful thinking/planning.
That leads to, if not the Qatar state, where is the money coming from, frankly I have zero idea. It's naïve to think it's definitely coming from the state, I trust the process will know. I do have concerns, one being a comment from HBJ, where it is reported that he labelled United's operating activity to marketing (what new marketing?), and I have questions about how such wealth was gained. Equally I have concerns about INEOS. Some have said both bids don't seem entirely clean, it's hard to know.