NBC merged/shut down NBC Sports Network earlier this year and moved their key sports properties to USA. They are mirroring TNT. They figured out they can demand more money for their flagship cable channel with sports than they could with USA and NBCSN. To be determined if that will bear out as true. They also moved much of what doesn't make it to USA to Peacock to bolster the streaming offer. They never had any college football on NBCSN as far as I recall because Comcast only has ND home games. And those go on Big NBC. I think I recall one, maybe two Domer games were on Peacock this past season. Joe can correct.
For those of us that watch stuff that was on NBCSN/now on USA, it's relatively seamless, but a lot less pregame and replays. EPL, golf, Tour de France, NASCAR, etc.
So if they got more CFB content beyond ND, it'd go on Big NBC, USA, and Peacock. They probably won't get enough CFB inventory to need to use their other channels. Golf, Univision, CNBC, MSNBC, Olympic, etc. For the last day of the EPL season, when every team starts at the same time to alleviate tanking and cheating, they will air them all across these networks and try to make a big deal out of it. But I'd guess they will stop doing that and push it all to Peacock.