I started hosting a set of web apps at fly.io about a year ago, and for the most part loved their developer experience. Publishing an application was a quick command-line operation, similar to heroku.
But after months of running several small-scale apps on fly, I've found that their platform just isn't as reliable as I need, so unfortunately I've had to migrate to something else.
The most frequent issues were just random downtime, usually caused by network flakiness somewhere in their infrastructure. I'd get alerts from a monitoring service, and at least one or two apps would be unavailable for a while. The down time was usually brief, maybe 10 - 30 minutes, but once or twice was at least an hour. I need more reliability than that.
So for now, I've migrated everything back to a Digital Ocean VM that I'm managing myself. I've had really good luck with D.O. over the years; I've run multiple apps there, too, and had rock-solid reliability.
The downside of running a VM is that I have to manage the VM myself, and deal with deploying apps there, or at least configuring github build actions to deploy there.
I'd like to get out of the business of managing VMs myself, so I'll be experimenting with some other platforms as well. First up is Cloudflare. Their Pages platform looks interesting, and remix supports it as a target platform out of the box. If that works, it should give me reliable deployments with all the ease of fly but with much more solid reliability.
I'll still keep an eye on fly; I really liked them in a lot of other ways, and hopefully they'll get their infrastructure to stabilize more over time.