How to stop the annoying moisture detected at the USB charging port.

You could have dirty contacts in the charging port. I work in a very dusty paper mill and I'll get a moisture warning when the charging port gets dirty. Use 90% isopropyl alcohol or electronic parts cleaner and a toothbrush to clean the port. Then blow it out with canned air if you can.

Use Android System Recovery Option to bypass Moisture detected at 0% charge.

I found a easy solution to this.

I had the same problem for months on my Note 9, tried everything you can find to fix it online, even had it diagnosed as having a bad charging port that needed replaced by a Samsung certified repair facility. Thank God I didn't go through with it. I use wireless charging everywhere. A couple places in my house, at my desk at work and in my car. So I honestly never needed to charge through the cable. But the fact that I couldn't hook my phone up to my laptop to transfer files or anything where I would need to hook to my pc (ADB, etc) irritated me. Back in June my phone had an update, not the One UI update, got that a while back, but some “bug fixes and security" update (6/14/20). Since that update my phone has been working perfectly. Glad I didn't fork up the cash for the charge port replacement! I feel bad for those that did and were also told that was needed to fix the problem! Pretty shady if you ask me. All good now though…