Doing fine till May 2019 update Windows 10 Build 18362. 400 Mbps connection, everyone else on my network fine but me! I'm getting 30Mbps speeds.
Realtek Gbe adapter. Gigabit switch, gigabit router, gigabit cable modem (interface)
After doing "all the things" (driver update, unbinding all the unnecessary ms stuff, resetting network, blah, blah) I found this and it worked for me.
In the advanced settings of the ethernet adapter disable:
all the offload functions (TCP checksums, UDP checksums, Large Send offloads)
Receive Side Scaling
Flow Control
Green Ethernet
Energy-Efficient Ethernet
Interrupt Moderation
Jumbo Frames
ARP Offload
NS Offload
Power Saving Mode
Now getting full speed. Hope this helps someone!