You can generate your own keys. Here are two PDF links I copied just now from a post I made 2 years ago here. I don't keep these white listed, so I did not check them for connecting. The first is the official UEFI overview. The second is a great guide from the US government detailing exactly how to set the keys. If that link doesn't work, pull out the document number from the link and search for it. Gentoo and Arch have guides on this. Fedora has the most advanced pre Linux init system in my opinion.

https://uefi.org/sites/default/files/resources/UEFI_Secure_Boot_in_Modern_Computer_Security_Solutions_2019.pdf

https://media.defense.gov/2020/Sep/15/2002497594/-1/-1/0/CTR-UEFI-Secure-Boot-Customization-UOO168873-20.PDF

If you have secure boot enabled, and you are using the shim from fedora or ubuntu, then yes you need to worry about it if you want to dual boot with w11.

I remember reading a post on mastodon where it was explained that no mother board validates the secure boot keys expiration dates otherwise it wouldn't boot the first time the BIOS battery gets empty and the internal clock gets reset. The post was written well and was citing some sources. But I didn't try to verify these assertions.

Pros and cons of disabling the default Microsoft key:

(Assuming you have secure boot enabled, and want the security that comes from that)

pros:

• You control your own key and have full choice over what software can start up on your computer, software cannot be approved by anybody else.
• Your secure boot security model is not vulnerable to the risk of booting 3rd party software with known security vulnerabilities.
• Sophisticated attackers with physical access to your computer cannot carry out an evil maid attack on your computer and convince it to trick you or steal your data.

cons:

• You need to have software installed to manage the key. There is software available for Ubuntu and NixOS.
• There are many buggy UEFI implementations out there that require the Microsoft key to load built-in oproms during standard boot, potentially bricking your computer.
• Software that gains root access to your computer could steal your signing key, potentially negating the benefits of secure boot against non-evil maid attacks.