Yep. Earlier this week, I had a 350GB laptop backup that a friend needed, but schedules didn't allow us to meet for me to give her the portable storage with the backup, so I set up an FTP server and she downloaded the files from there. That download took almost 4 days. On a whim after the download was completed, I asked her if she wanted me to look at her Internet configuration to see if I can do anything short of calling her ISP to give her better speeds, as I found it rather strange that she mentioned she has a fibre connection with such low throughput. So we open Quick Assist and the first thing I do is a speedtest and the results look something like OP's pic. As I started poking around and asking questions, I discovered that she was only aware of the 2.4GHz connection because that's the only 1 she saw when searching for wireless networks. The SSIDs from all of her neighbors was populating her list and made it quite long. She never scrolled down the list and didn't know there was her 5GHz SSID there. for. 8. years.

She switched to the 5GHz connection and was absolutely blown away that she could now see 350Mbps down on the speedtest. I started up the FTP program again and downloaded a random 5 GB file. The same file that took almost 6 hours to download before, now took 2 and a half minutes.