I put in our privacy policy that customers will be notified if majority ownership changes, but had not considered advance notification of the ownership change.

Such a clause might work as long as it's part of the sale contract to adjust the sale price if any customers take that option.

Good luck enforcing GDPR against any of the malign actors you should most wish to enforce GDPR against

Facebook and everything associated with it is doing everything they can to be and remain GDPR compliant.

Facebook has already been fined under the GDPR so it looks like that enforcement is working.

… What? No, they aren't. https://ruben.verborgh.org/facebook/ Clearly less than "everything they can".

Did he complain to the local DPA?

If not that's an excellent example and it may lead to FB being held to account.

DPA's typically do not go on fishing expeditions, you have to alert them.

I Googled around, and I cannot find any significant fines Facebook has faced for violating GDPR. The enforcement tracker you yourself linked (https://www.enforcementtracker.com/) only has one irrelevant entry for Facebook, and this feed (http://newsbreaks.infotoday.com/NewsBreaks/GDPR-2020-Where-C...) which was last updated just this August says litigation is pending.

If you have any sources for this fine, please post them.

I split my comment into two parts, since this one is more my personal opinion, and I don't want it to colour an otherwise straightforward request for sources.

From noyb's fight against Facebook (https://noyb.eu/en/open-letter), to me it is very clear that Facebook does not intend to comply with GDPR. They are actively trying to find loopholes, and according to noyd, also working with the Irish DPO to find and exploit loopholes. It is also worth noting that the total fines Google has faced from GDPR enforcement come to just under EUR 58 Mn (http://newsbreaks.infotoday.com/NewsBreaks/GDPR-2020-Where-C...). 58 Mn is chump change compared to Google's total revenue, and unless the threat of the full 4% turnover fine becomes credible, I doubt it will lead to any better action.

Wait, wait, wait a minute. In the same comment, you are claiming that Facebook is GDPR compliant, and that Facebook was fined for violating the GDPR. It sure seems like there is a major contradiction between those two.

Errm. No. In the same comment I am claiming that Facebook has already received a warning fine and that thus they stand to lose a lot if they are found to be in violation. I am not saying they are GDPR compliant because I can not know that with 100% certainty, but I'm sure they are doing what they can to not cross that line knowingly.

Facebook, Google, Apple & Microsoft are arguably the companies that stand the most to lose from GDPR enforcement, you can bet that they are well aware of this.

They're trying to stay fine free while also violating the spirit of GDPR as much as possible, since their business hinges on irresponsible and invasive data gathering.

Facebook is not GDPR compliant at all. The only reason they appear to be is that there is no enforcement of this regulation so nobody is actually looking at what they're doing.

There is plenty of enforcement of this regulation:

https://www.enforcementtracker.com/

Facebook has already been fined, and if they cross the line again they will be fined again, and quite possibly much higher.

If you know for a fact that Facebook is in some way or other currently not GDPR compliant then I would invite you to contact your local DPA.

There's no mention of any enforcement against Facebook on that website, except for one by the German DPC of EUR 51,000 for failing to notify them about their DPO.