I got the One UI 3 update last month on my Note 10+ and after that My Files app not showing anything in the Data and Obb folders. Other folders related to many apps aren't showing any files in them also. Any docx or other file is not showing in My Files app after saving. I don't know if it's a bug that is not fixed. If someone knows about it please give a reply.
I also recently updated to Android 11 One Ui 3.1, I got the solution. Download ZArchive from play store, when you first install the app, allow ZArchive to access photos, media and files on your device. Next head to Android data, now ZArchive will ask "For write data to the external SD card Android/data you must choose a path to its root directory". Press Ok. After pressing Ok it will open your internal storage Android > data. Use this folder. Enjoy and I hope this works for you as it worked for me 💪
