@externa1
i have tested it and it doesnt work for me too.
The public-folder-calendar is displayed in my EAS profile on my samsung device but using it in the stock calendar app shows the same problem.
I have tried to use your google-calendar-app too but it hasnt implemented a own EAS-connection as it uses the already synced calendars from the mobile.
So in my case the problematic samsung-eas-implementation and so it doesnt work there too.
So at the moment it looks like there isnt a good/working way to use more than one calendar on samsung devices with grommunio. (except of buying many user licenses and create many accounts)
Do you have a samsung device or another?