Dear RebornOS Community,
If you see that your timeshift always starts in the “Live USB Mode”, run the below command on a terminal:
yay -Sy aur/timeshift
This will update timeshift from the AUR, whose package recently received fixes from Git. timeshift should run correctly after this 
…
Thanks to @SoulHarsh and @damian101, this fix has been tested to work 
.
The reason for the problem is because the latest version of util-linux package, specifically the lsblk tool has had changes which break timeshift versions 20.11.1+3+g08d0e59-3 and below. This problem occurs if you have recently updated your system or if it is a new installation.
This manual intervention will no longer be required after RebornOS updates its repositories to include a newer version of timeshift from the AUR that has the fixes.