I am testing CoreELEC NG with KODI 19 on Sencor smp atv1 (S905x) and Mecool KM9 Pro classic (S905X2) TV BOXes. Everything works except backing up settings. I was used to the fact that the backup is 30 - 60 MB in size and the settings, accessories, repositories, etc. are backed up. In KODI 19, the backup is about 0.5 MB and there are no repositories, accessories, remote control settings, etc. Error or feature?
Try to update to latest nightly build and repeat backup procedure.
If still issue then collect full log after backup procedure.
In the version CoreELEC-Amlogic-ng.arm-19.0-Matrix_nightly_20210315 the backup is OK. Thanks