squeezing every last drop of resource form tired old hardware

This is such a myth. 99% of the time your hardware is doing there doing nothing. Even when running “bloated” services.

Nextcloud, for example, uses practically zero cpu and a few tens on mb when sitting around yet people avoid it for “bloat”.

Oh for sure - containers are fantastic. Even if you’re just using them as glorified chroot jails they provide a ton of benefit.

Containers run on “bare metal” in exactly the same way other processes on your system do. You can even see them in your process list FFS. They’re just running in different cgroup’s that limit access to resources.

Yes, I’ll die on this hill.

Could last years? Or months? Depends on a lot of factors. Fans may not like running 24x7, memory could fail, etc.

Just be prepared for what you would do if it does.

Since it’s a public instance you’d want to be sure to keep it pretty up-to-date with new system patches and the latest stable versions of Nextcloud. If you’re comfortable with automating updates with ansible, k8s, docker-compose, etc. then it’s not a big deal. If you’re ssh’ing to a server to manually update things then it’s going to be a lot of overhead and likely forgotten.

Old hardware may also bring its own issues and you’ll need backups especially since old hardware (especially consumer-grade stuff) can fail very unexpectedly. And providing support for users is a whole… other thing…

I like the idea of starting with the “old laptop in a basement” approach as a way to get things going to see if the service provides benefit then look to migrate to a more stable platform in the future.