I understand where you’re coming from, but we can see the trajectory of the Glazer’s ownership. Infrastructure is decaying, and while it can be patched, there will come a time when serious money needs to be spent. Based on their time to date the Glazers are unlikely to spend the 1-2B needed out of their own money and I don’t see how they can add that amount to the existing club debt.
A few years ago I would have been excited by Musk buying United. Great sponsorship opportunities from his other companies (at fair market value, of course), the best tech and some off-the-wall ideas to move football forwards. However, his takeover of Twitter has been unhinged and I dread those type of decisions at United and the damage they could do.
For me, and purely from the perspective of running the club (leaving other issues with their ownership for other threads), Qatar is much the best option of the ones you mention. I would expect that they will remove the debt, take no dividends and address the infrastructure issues. Hopefully they will also know what a gem they have in ETH and will back him with the players he wants rather than the biggest names.