Manhattan Beach just overturned their ban on strs & Hermosa Beach is pretty clear on their policies. 

With so many overturned sales these days, it's actually a known risk and not even that rare.

I have not seen a cert of title overturned by the owner during that window but have seen a case where the attorney representing the lender failed to show up at the auction to set the openinng bid and the property went for peanuts.

She failed to respond to the notice of review from CMHA to file an appeal to fight the rent increase so the decision could not be overturned. 

It took the state a year to overturn the ride-share fingerprint ordinance Austin enacted.

If not it likely can be overturned for lack of consideration.Did the attorney representing the LLC inform you that they only represented the LLC? 

Almost every PA court case overturning a tax sale is overturned on bad notice.In one case I researched, the judge overturned the case, because notice was sent to "Smith Debbie", and it should have been either "Debbie Smith" or "Smith, Debbie".Effectively there is not time limit on an appeal, only a time limit on the appeal AFTER the former owner finds out about the sale. 

That is exactly why courts will eventually overturn these laws, but much damage will be done in the meantime. 

Is there a redemption periodWhat are your rights during the redemption period.Generally anyone in the chain of title can challenge a tax sale. if it is overturned then you should get your investment back.

"blanket discrimination against felons"I think these ordinances will be deemed unlawful or overturned or changed and watered down to a point that they don't have any real teeth to the ordinance.A felon is not a federally protected class.Blanket is the key word you used which would imply SWEEPING discrimination which would be almost impossible to prove.A landlord would simply find another reason not to rent to them.Just like a contract there are always more loopholes to use if you don't want to do something.