A few weeks ago, I tested deploying Rails apps to Hetzner and Vultr for the first time using Hatchbox to deploy Rails apps onto them. I'm still supporting clients on Heroku, but there are potential new projects in the coming months that I might deploy elsewhere. Render is decent in some cases, but you can get a lot of bang for your buck deploying on Vultr, and Hatchbox makes it easy to do, whether you have one instance or a cluster. Hatchbox also helps with putting multiple apps/domains on a single server, a concept I had to give up long ago on Heroku. I've thought about deploying to DO plenty of times over the years, but there was always Heroku, and if I had to find a new home for Rails 8, I think I'd skip it in favor of a more powerful Vultr server. Hatchbox can provision Postgres for you, but Vultr has managed Postgres which is appealing to me. Or if you're just using Sqlite with Rails 8, that's easy to do with Hatchbox but not on Render since Render has an ephemeral file system.
Render lets you attach a disk to your app: https://render.com/docs/disks
Vultr is goated, I've been using them since ~2020 and have never had any issues. I stopped a year or so back and recently went through the whole onboarding process again and it was dead simple even 6 years later, with barely any price increase compared to other providers. Hetzner will always be the worst to me because plainly their UX sucks; I can't imagine if I was a non-technical user trying to use it