I have two s20 tags but my reader is not reading one of the tag’s serial number (UID). I don’t know what to do.
It is very sad you have some troubles but why you create another topic when you do not want give any additional information?
BR, Jan
Here is the link to the library you wanted. The tags you asked for are Mifare Mini S20 tags. Google it. You have internet don’t you…
Ok, thank you for the TIP but you are the one who has issue don’t you? Google showed me just topics around issue with some tags with Samsung Galaxy S20…
I see you are very clever and kind person so you will find it by your self with your good friend google and then it is not necessary to waste time here 
good luck with your project.
BR, Jan