Find an old Thinkcenter on ebay.
homelab
Yeah, this is my recommendation. I have a cluster of 6 little Lenovo Thinkcenters of varying ages. Some of them have been about the price of an rPi too.
Do you have any specific price/model recommendations?
Nope. Just get the best bang for the buck. If you really want two ethernet ports you can get a usb adapter. Or put in the time to learn vlans.
Update: I wound up getting one of the Chinese mini PCs from Amazon. $300+tax got me a Ryzen 7 5700U, 32GB of RAM, 1TB NVMe storage, and a single 2.5Gb ethernet port. I can add a second interface via USB-C if necessary. Really not bad at all. I have Proxmox up and running on it already, with PiHole and Jellyfin already running in LXC containers. Jellyfin took a bit of screwing around to get the CIFS shares from my NAS and hardware-accelerated transcoding going, but everything works now!