Second the NUC suggestion. I’ve got a 10th gen i7 model that I use primarily as a media server. It draws <6W at idle so it runs 24/7 and barely makes a blip on my electricity bill. It’s been rebooted exactly twice so far this year after switching from Windows 10 to Arch (BTW), once after a planned upgrade and a second time unexpectedly when my cheap UPS’s battery died. It works fine with the two docking stations I’ve tried and two different USB-C displays. I think my model might need a small adapter to support a third monitor but I’m not sure that’s the case with newer generations, though you may have to look beyond the Intel-branded hardware if you do want a more recent edition since they sold the brand to ASUS.
You may also want to look into NZBget (download client) and nzb360 for mobile management if you happen to be an Android user – or LunaSea either way.