When was this feature added, I cant see it in the changelog?

Hey there @Chaza218, I am so glad to hear that you're loving this new feature! Username suggestions come from the usernames within your current account. When creating a new entry, it will list your username options, starting with your most-used username at the top of the list.

This feature was first introduced in 1Password for Linux in early March of this year: https://releases.1password.com/linux/0.9/#1password-for-linux-0.9.27