@mrt10001 Thank you. I cannot install UT with an installer or inject it with fastboot as described at link text.
Now returning to latest Android 10.

Whoa, finally, Android 9.

@tassapan Still on Android 10. I'll take a risk try 191229.

@mrt10001 Thank you, but they are also on mirrors.lolinet. And I think they are newer than 200926. I'll try 200813 instead.

@mario-ch I flashed my device with file from mirrors.lolinet.
TB-X605LC_S100026_200926_ROW.ZIP
But I'm still on Android 10.
Where can I find an Android 9 firmware?

Model: Lenovo TB-X605LC
Android version: 10
Is it safe to downgrade to Android 9?