So what I did today was:
Pull a Raspberry Pi 4[*], 4GB, flash an Ubuntu Server 20.04.05, and go through the documentation for moving to another machine.
Mastodon & media: on a USB 3.0 512 GB SSD.
DDNS: ddclient (from GitHub) with CloudFlare protocol, and set up NAT rules at the router.
[*] Very much aware of brain farts of Raspberry Pi community manager + questionable path of the company, + also the deranged response from the co-founder. But I'm not trashing them all.
@gabriel I was going to install Mastodon on my server via Docker, but I got overwhelmed by all the fields I had to fill in, so I left it for another time.
Now, after reading this, I'm thinking that I should create a virtual machine to install it as the official documentation indicates.
@fonso_s it only took a bit of time to figure out the ddclient part, aside of the process of copying over all the media over rsync.
A caveat, be aware that the LetsEncrypt steps in the NGINX configuration are wrong in the official documentation. Follow this steps when you run into the error https://github.com/mastodon/mastodon/discussions/17372#discussioncomment-2045474