Apparently these talks have been going on for months. Interesting, at the SEC media days this week, the SEC stated that although it was studying possible changes in its conference scheduling protocols (going to 9 conference games or getting rid of divisions or both), it has "delayed" the study "due to the pandemic". Neither the SEC, OU or UT will issue a blanket denial. Rumors are that the SEC has signed off on it (except the Aggies, but who cares).
The risk to the ACC TV market will take a hit if OU and UT play conference games in Florida, Georgia and South Carolina.
If this actually happens, the affect on either Notre Dame or the ACC depends on what other parties do. In 2012, the Big Ten went after UNC, UVA and GT. But UNC balked because the Big Ten was not interested in Duke. Also in 2012, Texas boosters were making overtures to FSU and Clemson. The situation now is different. The Big Ten has the largest amount of students and alumni of any conference, but the southern TV market and population growth is far greater. You will have two major conferences, but the SEC with Texas and OU will be the clearly dominant conference.
Although the Big 12 has a GOR which basically prevents any member from leaving, the current one expires in 2025. The ACC didn't have a GOR in 2012, but it was signed in 2013 and was recently extended to the mid 2030's and many FSU fans are not in a good mood.
I cannot tell how this impacts ND. This potential movement of OU and UT into the SEC will suck all the oxygen out of the room and it will be dog eat dog as other conferences potentially re-align. There are 8 remaining schools in the Big 12 - such as Kansas, KState, Baylor, TCU, West Virginia, etc. Who knows what happens to them. Since ND doesn't seek to be in a conference for football, they are not doing any negotiating (presumably).
The differential in conference TV revenue per member, already an issue in the ACC compared to the other P5 conferences, will be geometrically greater.
I can't even think of all the issues this creates.