Comment 1 for bug 1822464

This bug is also present during 20.4 installation.

I have two ESPs on two different SSD drives. One used by Windows, another meant for Linux distros. Even though I mark Windows one as "Do not use this partition" during partitioning step, the Installer tries to mount it as /boot/efi anyway.

This is particularly troublesome if Windows taints the ESP somehow (like with Fastboot feature) and mounting process fails with the message:

"The attempt to mount a file system with type vfat (...) at /boot/efi failed"

resulting with whole installation process silently crashing (installer hangs on creating filesystems phase).

Possible workaround:

Boot into Ubuntu live environment with "Try Ubuntu" option, open GParted, unselect esp and boot flags for the ESP in question. Launch installer and make sure "Do not use this partition" option is selected for that ESP.