I use zabbix to monitor everything, agent on each device uses around 30 mb of memory and with the Linux templates it can monitor just about everything on the server.
I use Navidrome as the backend and DSub to connect to it. When I'm on the go I use a site-to-site wireguard VPN connection back to my server to listen to music and it also caches the songs so even if I don't have reception I can still listen to my music.