It's possible there just isn't a relay server sufficiently close to get a good result. Steam Link Anywhere doesn't connect the Link directly to you PC, it bounces off a Valve relay somewhere. So the 30km between you and the PC isn't important, what matters more is how far your Link and PC are from a Relay.
I'm in Newfoundland, Canada, and Steam Link Anywhere is functional, but adds a lot of latency. Judging from the round trip times I'd guess it's bouncing off a relay somewhere in Ontario or New York.
https://steamcommunity.com/app/353380/discussions/0/1680315447976235639/
[s:ac:哭笑]原来我能远程玩是因为这个, 局域网卡爆也是这个问题
一句话总结,你连接不上v社的中转服务器,用过向日葵远程控制就知道什么问题了。
解决方法:换宽带