This happened before, IBM sold global foundries to amd, who used it till they went broke and spun glofo off.
They had problems keeping up on tech, but they did spin a ton of defense silicon happily.
Intel fabs unleashed could be a second path, right now I would probably not consider a tape out to anyone other than tsmc, or maybe Samsung, but Intel might be an option.
The only issue is: I think they’d probably be assholes, I suspect they used to be to their internal customers, that’s why things like their fovea chiplets got caught for a decade in their internal politics during knights landing.
Tsmc are good to work with, you trust them and they try to make sure your design will work. Intel would have a lot of work on the libraries and other stuff (which they should have done more on with the altera integration) before I’d trust them to handle my design.
The smart move would be to work with some clients to generate portability libraries for their IP to make it easier to come over from tsmc.