Ubuntu 20.04 Network Performance Extremely Slow

The top voted answer didn't solve it for me and I got this solution from a different source.

This was because Ubuntu resets the TLP configuration when I upgraded from 18.04 to 20.04, and the power management went back to "on". I disabled wifi power management directly by editing /etc/NetworkManager/conf.d/default-wifi-powersave-on.conf and changed the value from 3 to 2, saved changes and rebooted.

could be the "backport-iwlwifi-dkms" package

I experienced a better performance without this package, so i suggest to remove it

$ sudo apt remove backport-iwlwifi-dkms

this is a known bug

https://bugs.launchpad.net/ubuntu/+source/backport-iwlwifi-dkms/+bug/1869588

Thanks a lot for all information you provided above.

Here I want to tell you about my situation.

I have an XPS-13-9360 (i7-8550U,16G,1T) and manually installed a killer 1650 (aka. intel ax 200). I was facing the same issue, extremely slow wireless connection.

And it seems that the problem has been solved since I installed a linux-5.6.7-generic kernel. (While the last one was 5.4.0-low-latency, I don't know why I installed low latency version, all that I did was do-release-upgrade from Ubuntu 19.10 with 5.3 kernels).

Here I recommend that you install a generic kernel instead of all one (by uname -sr, you can see what kind of kernel you are using), and upgrade to a newer kernel if possible.

BTW, I didn't sacrifice WiFi 6 and it seems OK with Linux 5.6.7

Bests, Leon