multiple errors when grub-customizer is launched

[Laskan]

I have recently update my Linux Mint to 21.1 from the 20 and I need to change the boot loader order because the first menu voice "MINT" doesn't point to the right kernel version.
I had to manually install the grub-customizer package from the PPA repo because it wasn't anymore supported nativelly by ubuntu/mint repo, anyway when I launch grub-customizer I get this error message: https://ibb.co/zhrHkzW

How can I solve it? Unfortunatly, since I have already used grub-customizer in the past now I can't find an easy way to edit grub without grub-customizer (can't identify right files to modify).

Thanks

[Daniel Richter (danielrichter2007)]

Hmm. I'm wondering the file /etc/grub.d/bin/grubcfg_proxy is executed when launching grub customizer. Generally it's reading the original scripts bypassing the grubcfg_proxy.

It says the script /etc/grub.d/bin/grubcfg_proxy became incompatible. That's a problem of older versions of grub customizer that copied a binary file to this location. Newer versions are using a better mechanic.

Try to fix it this way:
sudo rm /etc/grub.d/bin/grubcfg_proxy /etc/grub.d/*_proxy

Then you should be able to launch grub customizer. Some entries may be displayed as removed items. Make sure to restore them before saving the new configuration.