HA for personal MTA is way overkill, just run a second instance with higher MX record value. Antispam is a given, backups are snapshots, maintenance is just system updates. Of course, you could just run an appliance which does it all for you. I’d say it’s way easier than in 1990s.
Happily, I’m abnormal that way. I also dabble in PV DIY. Building houses from scratch, no. Servicing a modern car is also not worth it. Sadly, no open source EVs yet available.