Can you share a bit more about what you are trying to do? - like is it a new or an old installation? I have an assumption, but I prefers to know, rather than guessing …
Right - so you are in the process of installing Qubes on a USB drive (?) … is it the 4.1.2 release?
It’s been a while since I had an installer running … but I do recall having issues selecting the right options in the right order, to reclaim space … something with selecting the drive, click done, select reclaim space, delete all and then click done (?)
“error checking storage configuration” . I went into the setup and set the system reserve partition through the centos installer to standard partition and then mounted it with /boot/efi. I did not reformat it and I still got the same results. As this was puzzling me, I started thinking if this had something to do with the Secure Boot. Turns out it had to do with the settings of the CSM (Compatability Support Module). The launch CSM was set to Enabled so I switched it to “AUTO”. The message “error checking storage configuration” went away and I am now able to continue with the installation.