Samsung
Show or Hide Calendar Accounts auf Samsung
Samsung Calendar automatically lists every account linked to your device, including My phone, Gmail, your Samsung account, App Events and Reminder. This happens because One UI pulls in calendar data from all connected services by default, not because of an error.
You cannot remove an account entry from this list entirely, since each signed-in service keeps a permanent slot in the calendar app. What you can control is whether that account's events actually show up on your calendar view.
To adjust this, go to Tap on Calendar ➔ Open the Menu ➔ Choose an Account ➔ Show/Hide the Account. Repeat this for each account you want to hide from view.
Hiding an account only changes the calendar display. The account stays active for mail, contacts or other synced data unless you remove it from your general accounts settings.
If you want an account removed completely, including all its data on the device, do that through your accounts settings instead of the calendar menu.