Crypton uses +44 numbers for SIMs. I assume that’s because the UK country code is relatively desirable and, more importantly, the UK doesn’t require KYC for prepaid SIMs. If you don’t need their extra features, it’s functionally the same as going with giffgaff (if you have objection to buying another +41 line from your carrier), a well-known UK MVNO running on O2, topping it up £10 and using a little bit of data or making a call every six months to keep it active. It can be activated overseas as well as in the UK, last time I checked, which is quite rare. Crypton, however, costs more than a Proton Unlimited subscription if I understand their pricing correctly.