Yeah, so odd thing, I own a note 10+ and I faced the same issue. I plugged in a Kingston type c USB hybrid pendrive and there was no response from the phone. The even weirder thing was that I tried finding a solution to this thing online, but no one is talking about it, I tried searching for this about a couple weeks back but there was nothing. So I tried the pendrive with my friend's s10+ and I found the same issue. So apparently there is an issue but no one has asked anything about it anywhere online.
Have you tried looking under 'My Files'
I found my SD card there by scrolling past the internal storage etc until I found it. I was able to save the files I wanted by copying them to the sd card, then I used move file to SD card once I was confident it was working, thus freeing up space on my phone. Hope this helps.
I have used many USB drives and an external HDD on my Note 10 initially. But I noticed that after I updated to Android 10 beta and eventually to the public release, it always says that "there's an issue with the drive and needs formatting". This is bad on Samsung's part.