Oh. If you have systemd, you have udev. Then, you want to do the opposite to https://wiki.archlinux.org/title/Udev#Waking_from_suspend_with_USB_device (see last block in the section, tells you to add that content to the rule 50-*, switches to "enabled" simply put "disabled" instead). Sorry for linking to advanced docs. Hope you can make it and it really work out! Another option would be trying to install powertop, it has many switches but it's graphical and iirc had something to turn USB off... This approach would be more of a last resort, it's a bit of a hack to address your needs. Dunno if it would really work..!