Hello. I have constantly lost access to the Internet, although the WLAN is connected.
It should be every time re-connect.
Kernel: 4.18.0-24-generic
journalctl: wpa_supplicant[746]: wlp3s0: CTRL-EVENT-SIGNAL-CHANGE above=1 signal=-60 noise=-99 txrate=6000

I'm having a potentially similar issue (internet running about 1/3 the speed it should be). How do I tell if it's the same issue? I think my issue started after updating earlier today.

Ok, I figured out what mine was. It's an old bug I've been having with Ubuntu. The automatic DNS doesn't work very well at all. It was fine for the past few years, but I've had problems with it back in like 2011-2013. Changing the DNS to a different DNS (google's open DNS) fixed the problem. I don't know why the automatic DNS suddenly started acting up.