Did you remember to turn on OEM unlock or Android Device Bridge (ADB) setting on your device?
Also when you succeed flashing be sure to press VOLUME UP and POWER key during reboot or your phone will use the stock recovery software (I remember this was a headache before figuring that out!).
I succeeded installing TWRP. Thanks guys !
I'm not sure if my problem was the ADB option unchecked or more my USB port not to his liking (Even I flashed all my last phones through it).
I'm ready to prepare the next big step.
I'll start now backing up stuff (and buy some flowers to support the process of change ).
And of course, I'll go with LOS 16 as it seems quite stable :good: