I'm completely biased as I work on the nanos/ops unikernel toolchain but unikernels offer a very PaaS like feel as the app and server become one. You simply build your image (ops image create) and then deploy it (ops instance create) - two commands. Takes tens of seconds to have something running on AWS. If you are on a AWS/GCP free tier it costs nothing but even a a g1-small costs only ~$20/month and a f1-micro goes for ~ $5/month which can go a long way. We've had a go unikernel be on the front page of HN on a f1-micro and it barely registered any resources being used.

Besides the perf/security boost you aren't locked in to anything. You could take the same application and deploy it to multiple clouds simultaneously if you wanted to as it is making use of cloud primitives - nothing cloud-specific unlike some of the various serverless offerings.

Run dokku, caprover (or write a better heroku alternative, I'm sure now would be the time) on another free cloud service. I wrote a comparison of a few major ones: https://paul.totterman.name/posts/free-clouds/

AWS beanstalk allows you to run on very cheap instances, even cheaper if you get a plan and commit to a term.

It’s not a 1:1 experience, but I’ve enjoyed it as an alternative to Heroku for sure. Alternatively, you could spin up a server and install dokku which is pretty close to a shipping experience, but still requires some maintenance and hand holding.

GCP Cloud Run is very inexpensive if you use docker.

With some investment in infra as code we have a similar experience on aws. GitHub actions + terraform targeting ECS on fargate (pay for usage). Push to main build the container, pushes to elastic registry, makes the task/service, configures alba, etc.

Maybe you could try the auto idle heroku add-ons?

porter.run, convox, render, fly.io, dokku...

Have you considered Cloud Foundry?