Self-funded, digital, small imprint etc are options, but that really doesn't fit with the last few decades worth of releases.
Considering some of the people involved with the album, I'm surprised nobody has found a solution, but (as with a lot of things) this may just be Morrissey being obstinate more than anything else!?
Perhaps I'm being totally naive here... but maybe there's a scenario where he puts BOT on streaming services like Spotify, and optionally makes the digital files available to buy/download for $5-$10. So now the music is out there being heard and we didn't lose years waiting - great, mission accomplished. Perhaps mid-2022 or so he tours. Maybe based on the streaming numbers, tickets sales, etc. it's enough to generate interest and a record deal is forthcoming for the material post BOT?
While all of the above seems possible, as @Famous when dead pointed out, based on past experience he'll wait it out for years if necessary until there's a deal. Totally his call... but it just seems like such a waste especially at this later phase of his career.