I installed Zorin 18.1 on an external SSD and I am having issues with low download speeds. Download speed is around 20Mbps compared to my Windows 11 machines with over 300Mbps. I was having the same issue with Mint 21.3 until I downgraded the kernel to 6.14.0-29. The ZBook has an Intel 8260 WiFi adapter installed.
Have you tested this kernel on Zorin OS 18, yet?
Not yet. I have not found out how to change kernels in Zorin yet and I have been told that kernel is no longer supported.
I just tried Zorin in a EliteBook made it 2022 and same thing very low download speed and I would not call a PC made in 2022 old.
You can try 6.14.0-27 or 6.14.0-35, they are still there in the repos
The command is e.g.
sudo apt install linux-image-6.14.0-27-generic linux-headers-6.14.0-27-generic linux-modules-6.14.0-27-generic linux-modules-extra-6.14.0-27-generic
Then reboot and at Advanced options for Zorin select the 6.14 kernel to boot from and test the wifi. If it is better you can set this kernel as default to boot. Or alternatively, try the 6.8 or 6.12 kernel.
You could also test if it helps to disable bluetooth, maybe there are interferences. Or try to set the power profile to balanced or performance (if available) to see if it makes a difference.
Also disable wifi powersaving
sudo nano /etc/NetworkManager/conf.d/default-wifi-powersave-on.conf
and set there
wifi.powersave = 2
instead of wifi.powersave = 3.
Press ctrl+o, then enter to confirm, and then ctrl+x.
sudo systemctl restart NetworkManager
If you have a Dualboot with Windows disable fast startup at Windows power options and fast boot in your BIOS.