"Unable to turn on Home Sharing"

One Macbook Air M2 running Mac OS 15.1.

One iPhone SE 2nd edition running iOS 17.6.1.

both signed in to same apple id icloud account.

(!) The iCloud account is set up in "Advanced Data Protection" Mode.

both deviced are authorized for iTunes / Music purchases, i.e. I can play purchased music on both devices.

no Apple Music subscription.

The Macbook Air is brand new (refurbished), only been in use for a few days.

I recently upgraded the OS to 15.1.

I manually migrated my itunes/music library from an older macbook running Big Sur. Migration of music library looks good.

on Mac OS (15.1) I go to Settings, General, Sharing and turn on Media Sharing.

In shortened the Library name

I checked the box "Home Sharing"

i checked the box "Device update play counts"

left "share photos" unchecked

i checked "Share media with guests" and selected one single (smart) playlist as source for guest sharing. (No password)

on an older macbook - before activating icloud "advanced data protection" mode, both home sharing and guest sharing worked fine.

now:

• iPhone Music App: my macbook media share show up under the name I specified. I click on it => "Unable to turn on Home Sharing". When I try again later it shows no error message anymore just spinning icon and nothing happens.

* on network media device (connected to hifi):

it can‘t find any media shares on the network (expected: guest share should show up).

again both these shares worked with older mac running big sur. But i didn‘t have icloud advanced data protection mode activated yet. Obviously this shouln‘t matter, but I‘m just mentioning it for complete context.

Is this a known bug of Mac OS 15.1?

could it be related to advanced data protection on icloud?

anyone else like to try to reproduce?