Yawn- heroku used to be my go-to but hasn't been for years.
.NET is the only (cross-platform) server runtime anyone should consider running Server Apps on.
Also see https://devcenter.heroku.com/articles/dotnet-heroku-support-...
Both scale to zero, are portable, and allow full use of your language/runtime/framework of choice. Take any app you are deploying to instance compute today and add a Dockerfile and ship it.
AWS App runner comes close, but doesn't have the option to scale to zero.