I checked this with my testStorage_API29.apk (→ GoogleDrive link above) an a Google Pixel 2XL (runing Android R, 11 Beta). It works without any issues (using TaifunFile & EFile extension).
→ @Taifun @vknow360
The folder
/storage/emulated/0/myDir
is created and the text files are saved in and read from this folder.
