I'd love to have a chat with you to learn from your experience if you are willing! My email is tom at etebase, please drop me a line (or let me know how to best reach you).
Thanks again!
Perhaps a straightforward E2EE toolbox could help companies implement their products rapidly so they remain complaint. Clearly this won't help fix issues like Microsoft 365 or GSuite (which need access to the plaintext for email and similar), but it might help some types of SaaS to thicken up their client application and prevent the backend having access to unencrypted data, thus making the transfer permitted.
I just want to echo the above comment around how most customers don't have the knowledge to understand the benefit of this, but hopefully this is changing as we see more strict enforcement of penalties for data breaches. Data is fast becoming a liability you don't want to have the ability to see, and systems like yours offer usable solutions for those who don't understand all the technology, but need a solution.
One of the people I talked to had been involved with a startup called Adrenaline Mobility which did something very similar, but ultimately ran out of runway and was acquired by Twitter. He told an interesting story about how they (over-)built a highly scalable service but had a really hard time selling it. Those who lack the training to know the difference between good security and hand waving didn't see the value, and those who did have the training and skills didn't trust a third party to do it right anyway.
Nonetheless, a lot has changed in the past five years, and end-to-end encryption is more widely appreciated now. I hope you have better luck with the commercial side of things; this looks like a very promising start.