I left Heroku in favor of just a hand-configured DigitalOcean droplet. I might try Fly.io but honestly, for what I’m doing, the flexibility of a full Ubuntu box is just too good, even in 2022.
Try Debian if you want everything almost the same as Ubuntu but without the bloat. Everything is faster. What it lacks in branding/marketing, it makes up for it in the speed. Also recommend FreeBSD.