@marci and what does the fqdn resolve too, from your ping its resolving to that
ping www.digitec.ch
PING www.digitec.ch (198.18.0.75) 56(84) bytes of data.
So clearly your never going to be able to go there if its resolving to such an IP.
The other question is how and the F are you getting any response from that IP?
64 bytes from 198.18.0.75 (198.18.0.75): icmp_seq=1 ttl=63 time=18.3 ms
I guess its possible your ISP has such a network internal to their network.. That would be bad practice for sure. But it is possible - but the bigger question is how/why your resolving the fqdn to that IP in the first place? That site for sure is not being hosted on such an IP. Even if was recently decided to make that public space now, kind of how 1.1.1.1 was once not valid public IP space, and now is.
In the current state of deployment if that was the case - it wouldn't work for pretty much anyone because it is still listed as bogon (which do not route on the public internet - or atleast are not suppose to). And if that is the case - why has arin not updated to reflect that it is now owned by company xyz, vs still listing it as special use space.
if I had to take a guess to why it works when you connect via your phone to some vpn, is your phone (different dns, doh maybe) or the vpn dns is resolving it to the correct IP, while how you have pfsense setup its not resolving correctly.
But no your not going to get there if it resolves to that 198.18 address. Since it is not valid IP, nor is even suppose to route on the public internet.