Hello,
I finally managed to :
- unbrick my phone again using MSM
- update to Android 13
- manually install the latest /e/ T version (I didn’t use fastbootd)
I made some suggestions to update the istall documentation : OnePlus - 8 - instantnoodle - Documentation Suggestions - #4 by thealpman. I hope they can be taken into account.
This video helped me quite a bit : youtube.com/watch?v=aiqslJOV1Bo
Thanks again Iain for your very useful help.