Interesting, had no idea!
scrubbles
My mind went to this one

Our dang crazy ideas like not wanting someone to choose between healthcare and going broke for the rest of their lives.
It's out of date, and in desperate need of a rewrite. PHP might have been an okay choice 15 years ago, but no one in their right mind should be using PHP for modern server development. (Yes I'm calling out Pixelfed too). With so many languages and frameworks, that's probably one of the worst right now.
Then it was proven that they don't really get modern infrastructure either, as their docker containers depend on stateful code, with combinations of environment variables and php files that need to be stored in volumes, and then plugins which are also stateful - meaning that on new updates they need to go through an "update" process. This is directly opposite of good practice as docker containers should be 100% immutable and be able to run just by using docker run. They also have required volume mounts scattered throughout the OS, it was just never designed with containers in mind.
I can't recommend nextcloud right now, it's incredibly brittle and slow.
Agree with others, if you try to do a replica it's going to be very inefficient, and your costs will be high. You're looking for a backup, then just nightly/weekly you perform your backups. Any blob storage then will do, just work out what pricing works for you. Just plan out how you'd do a restore in case everything came crashing down - from ground up how would you bring your services back online?
HDD enclosure is a fine way to start, as long as you know it has limitations. Eventually you'll probably need more storage, and it won't scale. That being said, you can get 26TB hard drives now, it'll be a while. Just make sure you plan out how to back it up. Remember the rule - if you can't afford to buy a backup then you can't afford to do the project. Make sure you have backups in mind.
If you decide to upgrade to a full NAS solution later also remember that during that migration you probably will need to use new hard drives while migrating as your current ones will need to be copied from to the new NAS, meaning you will probably end up with a few redundant drives. Not a huge thing, but there will be no "in-place" upgrade. It all depends on where you want your homelab to go in the future.
It's the party of pure selfishness, they do not understand empathy. Until they themselves are affected at all, they won't understand .
It's how it works, they convince you every week that you are the minority, no one is listening. You just never look around to see that the actual minorities are no where in sight
Did they own the libs at least?
Yeah Proxmox leaves a lot to be desired in terms of metrics. However, metrics are supported out of the box. Bad news, you probably won't get what you want within proxmox. Good news, you have another project you get to undertake! Hooray!
Like I said, Proxmox supports metrics out of the box. If you go Cluster -> Metric Server you'll be able to see that you can add a metric server. The first iteration I did with proxmox I added an InfluxDB container which then proxmox can talk to (yes they can be on the same host), and then proxmox will start pumping metrics into InfluxDB. (It uses Telegraf under the hood). Then, you can also run Grafana, add your InfluxDB as a data source, and then you have a sweet metrics dashboard. There are a lot of pre-built dashboards already made that look great, and you can customize from there.
You can also use Graphite, I personally haven't used it, but I also dropped Influx over time too. These things evolve in that sort of way. That's how I'd get set up and started though.
It depends on your setup of course, many ways to skin that cat. You didn't really say where you wanted dashboarding. Do you want it through a terminal? Through a UI within proxmox? Personally I took it as an opportunity to learn Grafana and hosted it
This looks great! Thank you for the recommendation!