They often have security questionnaires you can complete instead. Or, as part of signing with them, you can promise to get SOC2 by x date (which will hopefully be easier with the funds from an enterprise contract).
I’d recommend looking online at some example security questionnaires or the types of things soc2 covers and writing an internal security doc for yourself so you know your position on everything and don’t have to scramble when it comes to it.
Just focus on providing a good value application and be frank about what you do, why you can't get certification for something like that, but that you can answer any questions they might have for their own certification process.
If the potential customer makes 'has SOC2' a requirement, than that is not a customer for you, in the same way that 'has more than 20 employees' rules you out.
It's important to really understand how unserious SOC2 is.
At the moment things look a bit uncertain, we're both going to run into more and more situations like this but also hopefully lawmakers will eventually realise that this stuff just doesn't work for OSS code and orgs.