Hi Jeremy,
It's a fairly safe bet you're going to have to replace the screen.
It's not at all uncommon for a screen to sustain damage with no visible cracks in the glass. Underneath the glass is another layer of glass containing the circuitry for the pixels that light up, and that sheet of glass is very thin and very delicate. In addition, there are connections between the etched circuits on the glass and the flex cable that goes to the motherboard, and again, those connections are somewhat fragile as well.
As is the case with most Samsung phones, you have two options when replacing the screen yourself; you can replace the screen alone by itself, or you can replace the complete screen plus frame assembly. The latter is the usual and recommended method, as it assures you that the screen is properly glued down and sealed to the frame. so for long-term stability that's the best choice. The downside to that method is that since you're replacing the frame, you basically need to gut the phone; remove everything inside the housing and transfer it to the new screen+frame assembly. Here's a YouTube video that steps you through the whole procedure.
Galaxy Note 20 Screen Replacement
The other method is to replace only the screen. You'll save a couple of bucks (not much, really, though) and you don't need to go through the process of removing and replacing everything, but you will have to carefully glue the screen back onto the frame after cleaning it thoroughly from the glue holding the existing screen in place. Here's the iFixit guide showing you how to do that.
Samsung Galaxy Note20 Screen Replacement - iFixit Repair Guide
I note that when searching for Note 20 parts and information, there are at least three other models that have similar names, so you'll definitely want to verify the parts by using the model number; on your phone it should look something like SM-N980F.
As far as finding replacement parts, they're still a bit pricey, being a large OLED display and relatively recent. As I mentioned, you can get them with or without the frame; the price difference is usually only a couple of dollars so it's really not enough to solely base your decision on. I usually start with places like Amazon, AliExpress and eBay, depending on how much you're willing to pay vs. how fast you want it. Here's an example of one that came up on my rather cursory search.
Super AMOLED For Samsung Note 20 LCD Display Touch Screen Digitizer Assembly Note20 N980 N980F SN980F/DS Replacement Parts
So if you're going to do this yourself, you'll need to decide which repair you want to tackle. Despite having to move all the parts from one phone to another, it's actually not that bad of a job; nowhere nearly as difficult as it would be on something like an iPhone. For long-term reliability the screen plus frame repair is going to be a better choice, but that's not to say there's any reason to think you would have problems if you glue the screen back on yourself.
I'd say go through the video and the guide and decide for yourself which one is right for you. Good luck and let us know how it all turns out!
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