The 2FA must be disabled in order to access your DeGiro account. Currently, there is no other way to access your account.
It is also possible to add Degiro lines manually via "Side assets" if you do not wish to disable 2FA.
Disable on App
Go to your profile (top left)
Click on "Security"
Double Authentication
Disable 2FA
Disable on Web
Go to your profile
Click on "Security".
Double Authentication
Disable 2FA