I don’t know exactly what you want host but I have an old Fujitsu Q920 i5 with 16 GB of RAM and a 2 TB SSD drive which cost me around 200 Euro.
I’m serving around 20 services on it including Nextcloud, Navidrome, Paperless NG, Emby, Matrix, Friendica, Wireguard, Zabbix, DNS blocker and a few VMs. Processor utilization is around 5% most of the time and it uses about 8 GB of RAM.
I admit that Nextcloud could be more responsive and faster but for the family it is enough.
I haven’t exactly checked how much electricity I’m using but I would have noticed a bigger change on my bill.
For backups I have a remote node at another location that retrieves ZFS snapshots periodically.
Anyway. I have this setup for 2 years now and I’m happy. It does what I expect it to do.
As a side note. i use FreeBSD with jails and bhyve for this. A Proxmox running VMs with nested Docker apps may need something more performant so be aware.
I haven’t. They only provide docker deployment which I’m not fond of. If they would offer an alternative installation method I may would. Heard a lot of good things about it.
At present I use Nextcloud client on my phone to backup photos and the Memories app to nicely browse them.