Error installing 20.04 from USB on ASUS a54c

I am trying to install Ubuntu 20.04 on an old ASUS a54c laptop.

It had Windows 10 installed. The laptop was waking "fine" but it was extremely slow, so I would like to install Ubuntu 20.04 instead.

I have create a live USB stick using another laptop, with Ubuntu installed.

I managed (with some difficulties) to access the BIOS and start the installation. During the check I got a message about two files with errors. After that everything was going fine but I got an error message at the end "The installer encountered an unrecoverable error. A desktop session will be run so that you may investigate the problem...."

I attach the error message. It seem to suggest that the error it the CD/DVD reader but I am installing from usb stick. I do not think the laptop is damaged as it was working fine with Windows 10 (although it was slow).

I have already tried the solution suggested here: The installer encountered an unrecoverable error and will now reboot

Any suggestion is welcome!