OK, so there's a lot of misinformation going around on here, so I'm going to try to clear the air and give my experience of what works and what doesn't on the S21 (FLAT) screen, and we can assume the same thing for the S21+. THIS DOES NOT INCLUDE THE ULTRA, which still needs the LOCA/UV protectors due to the curved screen.

First things first, how I add my fingerprints: I follow the method everyone recommends, which is using the lightest pressure possible to register your prints, so you can ideally tap the display to unlock your phone. I do NOT press as hard as I can, because, honestly, who wants to do that every time they unlock their device?

I register my right thumb 3x and my left thumb once, getting all areas of my right thumb scanned (tip, sides, towrds the tip, towards the knuckle, etc)

OK, so what I've tested so far:

• Ouba tempered protectors: https://www.amazon.com/gp/product/B08RDR1394/

These work. Not especially well, but they work. You have to jam your thumb down ONCE when registering your prints, then light taps work after that. This constantly gives the "cover the entire sensor area" when registering, and when you unlock, your thumb has to be in a pretty precise spot. If you were DEAD SET on tempered, I'd get this, but I still wasn't thrilled.

• UniqueMe Protectors - https://www.amazon.com/gp/product/B08R8ZPC34/

Worked about as well as the Ouba, maybe a little worse. I wasn't happy with these at all. Tore it right off.

• AmFilm "Hybrid" glass, designed to work with fingerprints - https://www.amazon.com/gp/product/B08RYV6PD5/

First things first - These are NOT glass. They feel like glass on the phone, which is the most important thing, but they're not glass. Anyone who says screen protectors protect your screen from breaking are full of shit. They protect your screen from SCRATCHING, and tempered protectors do the best job of that. I don't know how well these will resist being scratched themselves, but they feel great. It does NOT feel like plastic.

Now, as for how well they work? Perfectly. Like there was nothing on your screen in the first place. Fingerprints were registered quickly, easily, and the slightest tap unlocks the phone. This is where it's at. The protector is also super thin compared to the others, and really feels like a bare phone. If you use a case, you won't even notice it's there.

Edit: Man, this thing collects fingerprints like it was its job. Do NOT expect any sort of oleophobic coating. Still works great, but it gets smudged quickly.

Now, because these are clearly NOT glass, I can't say how durable they will be and how long they'll last, but recently they were on sale for $4.50 for a 2 pack. Well worth the money.