I got this working. Leaving the procedure I followed for others:
(Check prerequisites like unlocking the bootloader)
1. Flash the stock recovery (called stockoreo.img, just search for it in the forum) using fastboot.
2. Go into recovery, factory reset and clear cache.
3. Flash Dil3mm4's TWRP.
4. Proceed with the Original Post (I did not install gapps).
Wow ! I tried everything, I had bootloop, system ui crashing every 2 second, all the problems in this thread... until I read your message and guess what? it worked!!! thank you so much @royalford for this working workaround and thanks @DarkJoker360 for all your effort to make our PRA-LX1 still alive!
Btw, if you need some free coffee, don't hesitate to fix your "donate to me" button, it is not working