It's only really usable for anything that doesn't involve secrets, I'd be very concerned using anything third party in CI, let alone the runner itself. Supply chain attack senses tingling :).
Yes I totally understand the concern. We are actively working on SOC 2 and other compliance stuff to help with this. But honestly I feel the compliance requirements are weaker than what we actually implemented. For example proper secure boot and whole disk encryption (without sacrificing performance) are mandatory in our mindset but these specific things don't get reflected in compliance.
Instead of being a service, I'm also open to sell the software+hardware solution behind it, so you can have it on-prem. Do you think that's something you would consider given the constraints on supply chain security?
We're too small for on-prem services, so not your target market, just shared my 2c as someone who had been burned by self-hosting github runners too many a time.