...doesn't say what flash-all.sh had said before it got stuck.
It didn't print anything to the screen.
Maybe also report details of your machine configuration(s)? Which version of Ubuntu, which version of Fedora, how much RAM on the machine, how much free disk space?
Initially I tried my Windows 10 desktop (32 GB RAM), when that didn't work I tried my Fedora 37 laptop (16 GB RAM). Both have several hundred GB free disk space. When I saw that Fedora wasn't an officially supported OS, I tried an Ubuntu 22.04.2 LTS Live CD on the laptop, which is what ended up unlocking the bootloader. That's where I ran the flash-all.sh
I tried the chat room first, and one of the people there walked me through a bunch of troubleshooting steps, but nothing worked.
Try opening Device Manager in windows when you are in bootloader and see if there an device as Android with a warning symbol.
There was a Pixel 7 with a warning symbol. When I booted the phone to the stock Google Android, the warning symbol went away. I checked Windows Update and it had optional updates for "LeMobile - Other hardware - Android Bootloader Interface" and "LeMobile - Other hardware - Android Composite ADB interface", so I applied those. Now when the phone is at the bootloader, it shows up in Device Manager as an "Android Bootloader Interface", and now when the phone is booted it doesn't appear to show up in Device Manager at all.