Debian minimal netinstall should fit you use case. Long support time, small footprint and should support everything you want to do. Just secure it by having a unprivileged account doing all the stuff you want to do.

With that amount of ram you could make it a hypervisor and host a lot of containers and vms. Maybe proxmox would be a good fit?

Take a look at simple Android TV boxes with a USB port. There are plenty of options and you can just install vlc on them