Intel’s low power offerings are sometimes even less power hungry than a RPi and handle more stuff. I like Asrock’s line of CPU-onboard motherboards and use one myself. You get the convenience of a full x86 machine but it sips power. Mine peaks at ~36W with full load on CPU, GPU, RAM and 4 SSDs or disks. Usually it is much much lower. You can always go smaller with an Atom x5 z8300 (~2W Idle without disks or network, 6W with both and some load), but those are getting a little old and newer stuff is better and more feature-rich. Maybe an N100 machine with 4 or 8 gigs of RAM are a good option for you? Don’t go overboard with RAM if you are using docker for everything anyways. I use 8 but 4 would be more than enough for me and my countless containers. I run Nextcloud, Jellyfin, Paperless-ngx, Resilio, Photoprism and a few more. Only the minecraft server benefits from more than four. Very happy with my J5005 board.