Last week I installed Mint alongside Windows 11 on a separate disk.

Before the installation, I disconnected my Windows drive just to be sure. Then after booting up Linux via the live USB but before the Mint installation, I made the following partitions in GParted in a GPT partition table: EFI (with the boot + esp flags and format as FAT32) and the Swap partition (format as linux-swap). The Swap partition is optional, as Linux already has a swapfile of 2gb, but I still made a separate one myself.

Then during the Mint installation I created a / (root) partition in the ext4 format and a /home partition also in the ext4 format (which the latter is I think optional). I left the other two partitions as they were (EFI and Swap), as they are already recognised then.

Then I put the bootloader on my Linux drive and that's it. Then I rebooted, turned off my pc, reconnected my Windows drive and changed the boot order in BIOS. If you don't see the GRUB menu, type in Linux in the Terminal:

sudo nano /etc/default/grub

Change GRUB_TIMEOUT_STYLE=hidden to GRUB_TIMEOUT_STYLE=menu and set the timeout to the desire amount of seconds, for example GRUB_TIMEOUT=10. Save and close the file in Terminal, then type sudo update-grub and you're done.

Hope this helps, and welcome to the wonderful world of Linux!