I have a similar issue.
When downloading AIP or maps via WiFi (or LAN on my computer) in SkyDemon, it is unbelievably slow (maybe a couple 10 kb/s). If I switch to cellular it works fine. Tried with Windows, Android and iOS.
My ISP is Telekom and I have a feeling that it has to do with them. If I set up a hotspot with my phone and connect to it with my tablet, it is fast. If I connect to WiFi with Telekom ISP it is super slow. Tried at 3 different locations (unfortunately all Telekom ISP) with the same result.
Browsing, downloading anything else, etc. is fast. It is just SkyDemon where I experience the issues.
Any suggestions how I can resolve this?