Checking FritzBOX documentation it support IPsec VPN so technically it should be possible to get this working. Please keep me informed if you can get this done.
I could do some tests using my FritBox 7490 and fail on two different facts in the configuration:
- FritzBox dont support IKEv2 at the moment
- Use VPN tunnel as default route failed with error "IKE-Error 0x2026"
as long the IKEv2 cant be selected in any way i dont see a way to get this working.