@Jvan_Bontognali_Opif I completely understand your frustration, and I’m really sorry for the trouble this has caused 
Our devs have already made a list with the missing countries for the Phone field, and they’re working on adding them. If all goes well, they’ll be available really soon. I’ll update you right here as soon as I hear back from the team.
As for your suggestion to choose which countries should appear in the dropdown, that’s a great point! I’ve added it to our Wishlist - Option to choose which countries should appear in the Phone field dropdown . If more users support it, it may be considered for a future update.
In the meantime, if you’d like, our devs can help you exclude specific countries from the dropdown list using custom code. Just let me know which countries you’d like to remove.
If you’d prefer not to use the Phone field (even once the Swiss flag is added), you can opt for the Number field, as @Reinhard_Fust suggested. It works just like the Phone field did before the update.
I noticed you have around 40 Form widgets, and if you need any assistance with replacing the Phone fields with the Number fields, just let us know. We’re happy to help!
However, we’re hopeful that the devs will be able to fix everything soon, and that you’ll enjoy the new features to the fullest!