Looks pretty straightforward, every cable appears to be labeled with a location. It looks messy, but that’s just the patch cables that probably need some Velcro to be tidied up. It appears to be phone lines, data lines, and cable hook ups.
Looks like you have two unmanaged switches patched in to your data patch panels. You’d need to hook up your router or modem to one of the switches (since they appear to be connected) and you’d have internet at each port.
Same for your cable, looks like they run to a coax splitter and one is labeled satellite, you’d either need to get new service to the satellite or get a service box installed and connected to the splitter for cable at each location.
Phone lines appear to run back to the garage. Need service turned on there for phones active in each room if you still use that.
If you called whatever your preferred service was to active a new account and you told them the house was already wired, they’d have no trouble setting you up.