I had the same dilemma. It comes down to this in my opinion:

• Do you trust yourself and your current networking gear, software, security setup enough to host this yourself at home?
• Do you trust your vps providers tech stack, ethics, privacy policy etc. AND your own ability to secure it to host it on a vps?
• Do you trust Tailscale the company who’s in the business of “zero trust vpn” solutions to use their product?

I didn’t check if they were audited and if so how, but I went with the free Tailscale option, the most comfortable option for me now. Might change once I get more competent at the subject.

Since they are old, i would imagine the power efficiency isn’t the best on them for a 24/7 HA cluster at home. Unless you have an abundance of solar power or something. So I would use them as a test branch for whatever I want to do for self-hosting and learning

I would use them as learning platform for myself. Play with Active Directory DCs, replicataion, failover, recovery, networking etc. Just because more practice in that is what would be needed for advancement at work.

Others mentioned Kubernetes and Proxmox clustering. I could also use some sacrificial storage and compute to play around with those technologies so I could improve my self-hosted services.