I was able to unlock the bootloader with dc-unlocker. I bought 3 days license for ~$20 and it worked. I rolled back to the oldest (8-something) version with HiSuite and used software testpoint from dc (no disassembly or soldering). Just google for the tutorial. I spent two days playing with downgrades, testpoint enable and actual unlock (for some reason it did not work at first even in tespoint mode), but somehow I have bootloader unlocked now and can flash twrp, it stays unlocked after upgrading to the newest EMUI (only twrp can not read the partition then).