I did some more practical testing. I've added an additional IP to my existing server. No change, the issue is still there. Then I ordered a new identical server in the same data center, the issue is still there. Hetzner also has it's own download test file, I tried it and the speed was fine: https://speed.hetzner.de/1GB.bin . This makes it even more confusing.
So the only 2 remaining possibilities now are:
Incidentally, when you did those download tests from my server, was any one of them by just using Hyperoptic broadband? Unfortunately I personally don't know anyone who has Hyperoptic broadband to narrow this down to the final answer.
- Hyperoptic has serious peering issues with Hetzner
- Hyperoptic is throttling me to (a part of) Hetzner network
EDIT: I just got an account on IPVanish and tested with their NL based SOCKS5 proxy, the average sustained speed was about 90 MB/s. I still don't know who to blame, but I suspect Hyperoptic is at fault here.
Interesting that the hetzner speedtest server returns wildly differing results to your server. Does a traceroute to speed.hetzner.de return the same route as a traceroute to either of your hetzner servers? (Differing only at the very very end?)