Worth pointing out that while Forest were OK for Premier League PSR last year, they probably won't meet UEFA targets on either profits or football cost ratio, so they probably need to sell with being in Europe this year (hence Elanga and now potentially Gibbs-White).
They might have thought they'd get away with it, but the slap given to Chelsea and Villa has probably persuaded them otherwise.
And having been out of Europe for so long, it would piss off the fans mightily if they took the almost unprecedented step of not taking part, but as with Chelsea, if they don't sort their shit out they'll probably end up being fined more than they earn from being in the Conference League.