I did all the steps from the guide Btrfs system snapshots and rollbacks with Timeshift, but when I chroot in the new system to do the grub-install I get following error:
Installing for i386-pc platform. grub-install: error: install device isn't specified.
How can I do this grub-install?
I’m using the system with Legacy Boot.
Hi @phoeniqz 
,
Do you know which device you are installing the bootloader on? (they are usually named like sda, sdb, nvmexyz etc.). You may open gparted to figure out which device it is.
For example, if you find that you want to install the bootloader on sda, use
sudo grub-install /dev/sda
I have only sda with the partition sda1. Should I install it on the partition or on the device itself?
The bootloader installs itself at the beginning of the device. The program wants the device, not the partition.