Android 11: change ownership of media_rw files

Could somebody please help with the following problem on ArrowOS, Android 11? **Background** I use **TitaniumBackup** to create regular app backups. The TiBu folder is on **internal storage**. Then, after that, I use **Tasker/Termux** and the rsync command to sync the TiBu folder (among others) to my **external SD card**. **Problem** I got **error messages when rsyncing**: some files were not transferred - **permission denied**. I found out that the problem is **file ownership** - the files that can be transferred are owned by u0_211 which is the default storage app. however, those that cannot be transferred are owned by media_rw. I have no idea if this is some new TiBu behavior or whether I messed something up. As far as I know, media_rw is the **default user for stuff on external SD**. So something must be wrong here. At any rate, I cannot change ownership of these files even as the root user. **Question** Is there any way I could change ownership of these files? Or maybe some other solution/ workaround?