With offical smart phone flash tool I couldn’t flash the above firmware. So, coming from Stock Android 9-Pie, I did several OTA updates until the Stock Android 10 December 2020.
Then when the /e/asy installer failed and crippled my GS290, I flashed .img files via fastboot and was able to escape the /e/bootloop. But I don’t see this is an optimal solution for a user à la “Mom and Dad”.