I hit something similar recently, after installing Debian 12.8 (I think it was 12.8) on my wife's computer, where another Linux version was already installed.
I didn't find the root cause. I know it's a system on which SecureBoot used to be on and was working fine (with an older Debian version). Anyway after installing Debian 12.8, somehow I ended up at that infamous GRUB boot prompt, unable to boot the system.
I "fixed" it by disabling SecureBoot from the UEFI: not my proudest fix but I didn't feel like troubleshooting what had gone wrong (which was certainly simple and dumb). So Kudos to TFA's author for spending the time to troubleshoot and solve a much more complicated issue.
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I hit something similar recently, after installing Debian 12.8 (I think it was 12.8) on my wife's computer, where another Linux version was already installed.
I didn't find the root cause. I know it's a system on which SecureBoot used to be on and was working fine (with an older Debian version). Anyway after installing Debian 12.8, somehow I ended up at that infamous GRUB boot prompt, unable to boot the system.
I "fixed" it by disabling SecureBoot from the UEFI: not my proudest fix but I didn't feel like troubleshooting what had gone wrong (which was certainly simple and dumb). So Kudos to TFA's author for spending the time to troubleshoot and solve a much more complicated issue.