I had some problems with setting up ddns for no-ip. Long story short, the documentation is almost right. What I needed to do was install libopenssl, libustream-openssl, uclient-fetch, and ca-certificates before I can get everything to work right. The mysterious log entry with an error code of 5 was a hint but only after I read the source code for uclient-fetch.
Anyway if someone could update the documentation it would be great. Otherwise I hope when people Google they find this note.