Thank you for your help @harvey186 
I try that too but I unfortunately whatever the ROM I try to flash the result is the same 
Hello, i got strange errors flashing my sony XA2. Maybe this works on your device too:
type these commands in a console on your computer:
fastboot boot twrp-3.3.0-2-tissot.img (this will boot TWRP but not flash)
adb shell twrp sideload (this will prepare twrp to receive ROM)
adb sideload e-0.5-n-201905099519-dev-onyx.zip (you have to be in the directory where this file is)
Wait until it’s ready (if this works)
1 Like
My 2 cents: I flashed yesterday my OPX following this method without trouble. (twrp3.3.0.0)
Which version of adb are you using?
The only difference I notice: My working directory was /home/Download so I just type:
adb sideload e-0.5-n-201905099519-dev-onyx.zip
not the full path to the file
2 Likes
I also try everything from a PC instead of a Mac but no more success
I’ve been using adb 1.0.39 to flash, so I don’t think your problem is here…
In TWRP did you try to tap Wipe > Advanced Wipe, select “System”, “Data”, “Cache” and Swipe to Wipe
Yes Manoj thank you.
I follow the steps mentioned in the wiki https://wiki.lineageos.org/devices/onyx/install
The ‘Smartphone-mail-in’ program will start soon. Dates once finalized will be announced on all channels.
Thank you @manoj, I will wait with my brick until the program start.
Let me know if you need a crash test candidate 
CC. @GaelDuval
Hi @Sebu unfortunately we do not have a ETA as yet with the team busy with the development tasks. Will update once I have any further info on this.