I've triple boot in my laptop, The first instalation long time ago is Windows 7 then the second OS I was installed is Kali linux 2020.4. Then the last os I was installed is ubuntu 20.04 LTS. But problem is arise after restart from installing ubuntu, My lovely grub kali linux was gone. There is only two os listed. ubuntu and windows 7. I searching on the internet I found but not solution to my problem.

1. I boot with boot disk repair. it seems working but this distro erase my ubuntu grub and directly enter boot to ubuntu. In ubuntu desktop i type sudo update-grub and my grub ubuntu is back.
2. I found this video on youtube: https://**********i5yUfPtruIg
but stucked in sudo chroot /mnt , I've got this error message chroot: failed to run command ?/usr/bin/zsh?: No such file or directory. I follow this tutorial step by step with usb live kali linux 2020.4 and usb live persistence kali linux 2021.1 All stucked in that command
I use bios legacy and MBR.
My question is;
1. How to recover my Kali linux grub loader
2. How to run chroot smoothly in usb live kali linux or in usb live kali linux persistence in kali linux 2021.1

Please help me because I want to use My Kali linux again, I not yet found solution for this problem. Please share your knowledge if you know information to solve my problems. TIA

Best regards,