This started happening a few days ago. Whenever I load a website, it takes vey long. It took about 10 seconds to connect to wikipedia.org according to ping, when it usually loads instantly. According to speedtest.net I have high upload and download speeds, and very low ping (I attatched an image of the results). This happens in ungoogled-chromium, but I installed Firefox and got the same result. I didn't upgrade the system or change network configuration before this started happening. This does not happen on other dvices connected to the network.
EDIT:I removed the additional dns server from the advanced network configuration GUI, the problem is now fixed.
EDIT 2:It is slow again (a little less slow though).
Sounds like it could be slow dns ?
One ip of wikipedia.org is 91.198.174.192 .
try pinging the ip and if it's much faster than pinging the domain name then it is the DNS.
If so try another one
https://dnsprivacy.org/public_resolvers/
I tried the quad9 DNS servers, it seems to be fine now.