One place it would be useful is if you are worried about somebody breaking into your home and stealing your computer. Don’t store the key on the home computer, instead store it on a cloud server. The home computer connects to the cloud server, authenticates itself with some secret, then if the cloud server authorizes, it can return the decryption key.

Then if your computer gets stolen or seized, it’ll connect via a different IP and the cloud server can deny access or even wipe the encryption key.

this doesn’t protect against all risks, but it has its uses.

Example: https://www.ogselfhosting.com/index.php/2023/12/25/tang-clevis-for-a-luks-encrypted-debian-server

This is a good idea. It’s a lot easier to incentivize a maintainer who is already familiar with a project and invested in it with some money than it is to get a person who is unfamiliar with a project.

How much you should donate and how likely they are to agree depends on how complex your request is, whether they feel it fits in with the project for other people, and how busy they are.