@turtlenate

Wasted a lot of time over this issue with F5121 which was previously running Sailfish OS. In my case had saved TAbackup prior to bootloader unlock for Sailfish so downgraded device back to MM with Androxyde Flashtool, restored DRM (Androxyde Advanced settings), upgraded to stock Oreo, bootloader unlocked on latest firmware, turn on USB debugging, installed twrp-3.2.2-0-suzu.img, wipe then advanced wipe for cache, dalvik cache, data and system, fastboot flash oem SW_binaries_for_Xperia_AOSP_N_MR1_5.7_r1_v08_loire.img and then run UBports installer 0.14.4-Beta to install 16.04/community/fredldotme/devel and got "spinning white circle" this time. Remember to remove any microSD card for any subsequent OTA updates, now on v 10* OS build number 2020-01-01/2.