Co-founder of Nimbus here (https://www.usenimbus.com/)

We also provide a remote dev environment solutions. I think in your use case is very special as you cannot leverage any cloud providers, which can potentially make it harder for you to integrate with certain solution.

We are looking for design partners. If you like to share more and have a discussion, I am very happy to learn more about use cases and make Nimbus work for your on-prem infra.