First off, congrats on launching! I've personally been working on something very similar for the last bit, and actually plan on launching very soon.
As other commenters have mentioned, this is a system which seems all-to-common to have built in house, and I think you've highlighted issues with that: it may be simple to get something basic working, but without a larger investment, it ends up being unstable and unmaintained.
It's been great seeing all of the similar solutions being launched over the past month, and the slight different ways that different players (you, Okteto, LayerCI, Release, FeaturePeek, etc) are approaching this issue. I see that what you have done is specifically focused on Docker, and purposely avoided Kubernetes. I think that gives you a niche space, along with Dockup (https://getdockup.com/), who I believe are taking the same approach.
I appreciate your focus on security and privacy, specifically around "can never seen your code", but I'm curious about this choice. Did you find that this was actually a concern that customers had? CI/CD platforms, which are kind of a neighbor of Continous Product Review tools (this is how I've been referring to this class of product internally), and have an implicit trust. I have not received much push-back about automated code access, and when that has been a concern, I've found that those individuals preferred to how everything in-house anyways (Gitlab, or Github Enterprise).
Do you have any sort of cost-control structure in place? Being a Github Action, I see this more as a library than a managed service, which also means you have less control/ability to monitor your users ephemeral environments, and I would hate to see the shutdown behaviour break, and suddenly ephemeral environments never go away and your user is left with an obnoxiously large AWS bill.
Overall, I love what you're doing to approach this space in a new way. If you'd like to chat about the space, my email is in my profile (I literally just added it, so hopefully it's visible :fingers-crossed:)