I have a Toshiba dynabook Satellite Pro C50-A-1K9 laptop. It is dual boot system - Ubuntu 20.04LTE and MS Windows10.

After I did the latest Windows update, which included a Toshiba BIOS update to 1.80, the computer will only boot into Windows without showing the usual Ubuntu boot menu.

I ran the boot repair disk from a USB stick, but no change - MS Windows again

Whilst in Windows, as recommended by boot repair, I typed in the Windows command box:-

bcdedit /set {bootmgr} path \EFI\ubuntu\shimx64.efi

No change - it still boots into MS Windows.

I do have comprehensive backups of my data, but unless there is absolutely no other way, I do not want to start with a fresh install of Ubuntu as there is much software installed and the total size is 1.5Tb

I have been using Ubuntu for several years now and am familiar with the command line. However, this problem is way out of my league and I would appreciate the assistance of a systems expert! This page, generated by "boot repair" may be useful-

http://paste.ubuntu.com/p/wWjQhpn8N9/

It may also be helpful to those who are developing new versions of the boot repair software to hopefully overcome the problems caused by this latest unfortunate update from MS Windows.

Thanks.