We checked the frequency of the requests at N26. Unfortunately, there is no way on our part to influence the frequency of 2-factor authentication requests.

As a workaround, you can exclude your N26 account from the general account refresh:
'Settings' > 'Refresh Accounts' > 'Ignore upon Refresh' > 'N26: ON'

This way the account will no longer be updated automatically when the app is started, in the background when refreshing all accounts, and you will have to do the verifications less often. You will still be update refresh the account manually at any time.

If you combine all N26 accounts into an account group and update this group, only a single verification / TAN is required for the entire group.