

Yeah, I tried tuta. I have (overall less but) the same issue with proton. I just want to use my own client apps of choice.
I have registered with mailbox.org and while the trial period is very limited, the web ui is minimalistic and basic looking. You could say outdated. I seriously consider paying for a “team” account for me and my wife. The price is unbeatable. Aside from the gui, the features I need are there.
I just need the Wife’s approval. She’d be migrating from yahoo of all places.
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.