I'm a Lenovo m715q mini PC man myself, but I really do love the 1L form factor for home lab

Proxmox with various VMs is what I use, and I do like it. Also it's a very light OS, I have a 4c4t Ryzen chip running three Linux (Ubuntu and Debian) VM's running a few services and one Windows 11 (this is just to mess around) and at most 50% CPU usage.

If you want to still mess with containers you can use Prox, load up a VM, and then run containers in that VM.

You could likely find a Ubiquiti UDM pro on eBay for around or just under $200. It has a small amount of 10g connectivity and a built-in 8 port gigabit switch, and a really nice web-based user UI.

The minis can be had for 50-100 on eBay depending on model and specs. The larger desk tops are also probably in that range as well. I use the Lenovo m715q (also a mini 1L chassis) that I got for $85 with Ryzen 3, 256gm NVME, and 16gb RAM.

I got one of the Elitedesk mini PCs with a Ryzen 2400ge in it but was never able to get the bios to save any of my settings so I couldn't disable secure boot. So it's going to get turned into a chock block for my snow blower.