A family member was in the unfortunate situation that her Windows 10 Lenovo Thinkpad 13 was stuck in a boot loop, most likely due to a botched Windows upgrade. The problem could not be fixed using a Windows 10 installation media and the normal Startup Repair option, the BCD commands in the Command line, or restoring from older System images.
So I made a Ubuntu MATE USB stick using UNetbootin and a disk image from ubuntu-mate.org/download/amd64/. Booting from this stick I was able to access the hard drive. If I have had an external hard drive I could have backed up to this, but instead, I streamed a tar-ball to my home server using the command below. This has the benefit that I do not need to write a tar-ball first on the laptop that only has an OS in memory. This solution streams the data through the network to a tar-ball on the server.
tar cvz Username | ssh firstname.lastname@example.org "( cat > 2020-12-15-backup-windows-user.tar.gz )"
After this was backed up. I could reinstall Windows 10 on the laptop using the Lenovo Recovery Media tool. If that was not possible I would have used the Windows 10 installation media.
Post mortem The problem turned out to be that the SSD was broken. While it was still possible to read from it and writes were impossible, which in turn made it impossible to start Windows. After buying a new
Samsung SSD 860 Evo 250GB SATA6 M.2 2280 SSD I could reimage it using the Lenovo Recovery Media and copy the backed up files to the new installation.