IPv6 with CyanogenMod 13 and Deutsche Telekom LTE

After re-flashing my Moto G 2015 with CM 13, no IPv6 address was assigned to it for mobile data, neither on 2G, 3G or 4G. The APN i was using was "internet.telekom", and indeed the default setting is to obtain an IPv4 address only. However, even setting "APN protocol" and "APN roaming protocol" to "IPv4/IPv6" and rebooting did not help. WTF!!

The solution was to delete the APN completely and re-create it.

Unfortunately, I have not checked what exactly this changes in /etc configuration files, but as an easy solution it was good enough for me.