@MrT10001 I made progress. Now it's stuck on "deleting logical partition" for an hour :

The phone display the fastbootd screen :

@Moem I have no Continue button

I only have this :

@stanwood

It turned out that I had missed the "fastboot flashing unlock_critical" part. Since then - and after repair by Fairphone - I've made some progress: Now the installation begins, but the UBports installer gets stuck at the "rebooting to fastbootd" step, while at the same time, the phone already displays the Fastbootd screen, with the menu offering "recovery," "reboot to system," "reboot to bootloader," and "advanced. But nothing happens

@Lakotaubp I did have unlock the bootloader, and when I had the following picture, it showed "DEVICE STATE - unlocked" like the picture

I will try the FP4 telegram channel

@Keneda I got this on Windows

*** Fairphone 4 flashing script ***

INFO: The procedure will start soon. Please wait...
INFO: The package type is "user-factory"
INFO: The build number is "FP4K"
INFO: You are using MinGW on Windows

INFO: Validating the integrity of the package.
      This might take a while. Please wait...
INFO: Validation complete.
WARNING: Flashing this image wipes all user data and settings on the phone.
         It will also remove the Google factory reset protection.
         Are you sure you want to continue?
         Type "Yes" (case sensitive) and press enter to continue: Yes
INFO: Looking for connected device(s)...
INFO: One Fairphone 4 in fastboot mode found (serial number: *********).
ERROR: The critical partitions are not unlocked.
       Please refer to our support articles for help.
ERROR: Aborting now (press Enter to terminate).

I tried to contact Fairphone et write on the telegram channel, but did not have answer for both

@Keneda

Sorry, there ti is :

*** Fairphone 4 flashing script ***

INFO: The procedure will start soon. Please wait...
INFO: The package type is "user-factory"
INFO: The build number is "FP4K" 
INFO: Youre are using a Linux distribution.

INFO: Validating the integrity of the package.
      This might take a while. Please wait...
INFO: Validation complete.

WARNING: Flashing this image wipes all user data and settings on the phone. It will alse remove the Google factory reset protection.
Are you sure you want to continue?
Type "Yes" (case sensitive) and press enter to continue: Yes
INFO: Looking for connected device(s)...
INFO: One Fairphone 4 in fastboot mode found (serial number: *******).

Then nothing after this, the script ends here.

@Keneda I did,but manual installation ends without doing anything :

I checked twice I had take the right package, but it still ends like this

@TheVancedGamer Hi, I believed, at first. Then, i checked after my 1st failure, and the default OS was Android 12. So i tried to install android 11 manually, but it did not work ( processus terminated without any work).

"I tried to install Ubuntu Touch on my new Fairphone 4 with the ubports installer 0.10.0. Everything worked initially. The UBports installer indicated that the installation was successful, while my phone was stuck on "installing updates" for a while, then it restarted and has been stuck on the "Fairphone" startup screen since.

In the meantime, I tried to restart it, but it only alternates between the Fairphone startup screen and the screen indicating that the boot loader is active. Attempting to reset to factory settings didn't work, and neither did my second attempt with the ubports installer. I'm not sure what to do next."