This might be related to https://lists.debian.org/debian-devel/2020/07/msg00070.html
- Bug#1010992: sstp-client FTBFS on IPV6-only buildds Adrian Bunk
- Bug#1010992: sstp-client FTBFS on IPV6-only build... Jonathan Rubenstein
- Bug#1010992: sstp-client FTBFS on IPV6-only b... Bastian Germann
