I can confirm that Call Screening is currently not available for Swiss language variants - neither French (Suisse) nor German (Schweiz) are supported yet.
However, I found a workaround that made it work for me in Switzerland:
- Go to Settings > Siri & Apple intelligence > Language and change it to "French (France)"
- Go to Settings > General > Language & Region and set your region to "France"
After making these changes, Call Screening became available.
Apple hasn't announced when they'll add support for Swiss language variants specifically. It seems to be a gradual rollout based on language and region combinations. For now, if you need Call Screening and don't mind the regional setting changes, this workaround does the job.
Hope this helps!
Fred