Alias on FairEmail
First of all, you open FairEmail and go to "Create Identity" in the principal settings, point 2, by tapping on the "Manage" button (3 dots top left '>' Settings '>' tab "principal settings").
In the settings you'll tap and hold on your Disroot-Account until a menu opens. In this menu you'll choose Copy....
In the following input dialog you are presented an identity, which is connected to your existing Disroot account. Fill in your data or change the automatically filled information as you wish.
(Every Disroot user has an firstname.lastname@example.org alias to use by default)
Finish your input by tapping by tapping on the Save button at the bottom of the menu. Your ALias is now set up.
To send an email with your new alias tap on the From: field and choose the alias you want to use from the appearing dropdown menu.