According to stories released by the club they are always in FFP danger, Gibson allegedly puts the maximum in every season to keep them afloat. According to the old fellar they suffered historically due to wages agreed by previous regimes but that was all supposed to have been fixed over recent seasons. At one point the club owed serious money to Gibson's company, but since 2010 when they started yo-yoing a bit they got on top of their expenditure and debt, and I vaguely remember them having a relatively large negative net spend of around £30m since 2010. There has always been a suspicion, usually repeated every season, that Gibson is trying to pull out of the club and there is no denying he has reduced the club's debt to his own company in that time, which I think was well over £100m at one point, without spending as much cash as he once did. They were mental in the transfer market when the Premier League first kicked off though, it was like fantasy football for them.
Since 2020 their net spend has been more or less zero. Not sure how far FFP goes back, was it 3 years? I have no idea of their operating costs, but you can understand the fan's doubts since transfers are usually the biggest issue in any FFP issues. Especially when the club have been telling the fans for over a decade that they were fixing the debts.
They also had a Premier League season in amongst the last 10yrs so will have had that, plus parachute payments. They didn't go daft on transfers then either.