Hello @StefanN,
The mixer will always power up in the same state as it was powered down. This is a standard on A&H consoles.
It isn’t possible to configure the console to an specific user or scene to boot up.
The best solution would be to make sure that the Basic user is logged before shutting down or, if the intention is to avoid users to operating under the Admin user, then setting up a password on the Admin user which will force them to log into the Basic user at start up.
I hope this helps you!
Rafael