Having used Manjaro for around half a month now and also having switched from Windows, I’ve been getting slower download/upload speeds in Manjaro than what I used to get in Windows. This slower network speed extends not only to regular browsing but to everything else too, Discord calls, ping in games, watching videos on youtube, you name it. I don’t have the best internet ever but on windows I was managing ~18 Mbps Download / ~5 Mbps Upload while on Manjaro I am averaging ~8 Mbps Download / ~3 Mbps Upload. I have tried a multitude of things from changing my MTU to messing with my router settings but the difference has been miniscule at best.
Turns out it was not a Manjaro issue. The actual problem was that I had the antenna installed on the wrong port on the back of my router. I just installed the antenna on the proper port and that seemed to fix the slow internet speed.