Raspberry Pi 4 (with its linux distribution) and an external usb hard drive attached. Install whatever service you want on it. I have Jellyfin and openproject (previously redmine) on it. This mini thingy sits without monitor, keyboard or mouse somewhere next to my router and connected with an ethernet cable. Works flawlessly.
Could you elaborate a little bit about “full of bugs” and “non-obvious behaviour”? I use Ansible at work for a couple of years already and never encountered anything like that. (I have about 10 playbooks, about 30 roles, about 20 linux servers that I administer)