Actually, one of the hotels in question is in fact one of the hotels doing that.

I'd nail them to the cross for such questionable and shoddy practices but did they offer an alternate amenity or reduce the rate upon check-in?

I stayed at a property recently that had a Breakfast rate and the front desk handed me a $50 UberEats GC in lieu of the breakfast due to the restaurants being closed. I thought that was an acceptable work around.

So - somewhat related question.

Stayed at a Fairfield Inn for a week and they only offer "free breakfast" on Saturdays. Not a big deal but isn't that their schtick? The rates were no different for the other days.

How do you actually file the claim? I can’t seem to find a link anywhere.

Filing a claim=before you leave the property, tell the front desk the specifics of the problem, that you are invoking the guarantee, and want the cash.

They will typically say no or they aren't aware of this. That's when you need to speak with the duty manager or GM. If they turn you down, call Marriott and document it.

It has happen to me several times, but I have never knew to claim at hotel. I wonder if they would have said no or possibly said, "Oh yes we did" Usually there has only been one person on duty when I check in and I doubt they would wake up a manager for that.

In my experience brands like Fairfield or Courtyard (especially at the weekend) may not always have a manager at the hotel, but full-service brands like Marriott, Westin, etc. always have a manager or someone empowered to act as a manager working. The lone exception might be the graveyard shift. But always, always get the name and business card of the general manager and email them to document the claim, besides calling Marriott.

I wonder how people do this?

Do they wait until they are about to walk away and instead just ask at the desk then from the clerk?
Do they walk away from the desk and then turn around and walk back to the desk and ask the clerk?
Do they wait until the clerk is done and then ask for the manager?
Do they go to their room and then call down for the manager?
Do they wait until the morning and then make the claim?

just do it in the in app chat and screenshot

I have no idea what you mean by app chat.

As soon as possible. A front desk agent will often not know or not have the authority to do so. Have a manager contact you and do try to settle before checking out. I had to once sort this out after leaving the hotel and it was a major pita ... settled for points in the end.

that's another good way to have written confirmation of whatever they commit to

The Marriott app has a chat function where you can contact the hotel

Don't really care. For almost all of my stays, I check in, shower, sleep, shower, check out. I don't really want the to go bag anyway I have to throw away before going through security (liquids), since I usually get to the airport at boarding time, and a lot of times I leave/check out before breakfast start time (e.g. 6am)

So there is a way to chat with the hotel management while you are there and screen shot that you did?

On the app... chat function for your stay (although it’s probably not with hotel management directly but at least something in writing from the hotel side)