Did I miss some news or why can't I choose Swiss Francs CHF as a currency anymore?
Did GOG reduce the choices to €, $ and £ on purpose?

May be a geolocation bug? Did you check to make sure it still sees you as being in Switzerland (at the bottom of the checkout page, under the recommendations)?

And if it is such a bug, you may find it useful, seeing as Switzerland tends to get higher prices for everything.

-wrong thread-

What do you mean? I can only set the location in my settings and it is set to Switzerland indeed. I even changed it to Sweden and back to Switzerland to check, if a setting update would reset the currency.

I have the language set to German and the currency set to EUR for now.

The location you can set is just what's displayed on the forum, the one GOG uses to determine the prices you get and the available currencies (and also any blocked games) is determined by your IP. Since you get GBP as option, it seems it currently detects you as being in the UK.

Well CHF is definitely still available.
So it is probably like Cavalary says; a bug in the location detection.

You can put something in your cart and go the the checkout page. At the bottom it shows the detected location.

You seem to be using a proxy server (through a Virtual Private Network or the like) located in the geographical United Kingdom of Great Britain & Northern Ireland.

Thanks for all your inputs.

It was a cookie issue. I removed all the cookies and logged in again.
Voila, there is CHF again.