Welcome to the forum. 
Please post the terminal output of:
inxi -Faz
BTW, you don't need the internet to install Garuda, but it helps.
You can use Ethernet or USB Android phone tethering for an alternate internet connection. From years of network troubleshooting, I've learned not to waste my time trying to fix Wifi in the live environment. It's not that it's impossible, but if you need proprietary wifi drivers it's just far more trouble than it's worth.
After you've posted your inxi -Faz output I will have a better idea if your Wifi adapter is problematic with Linux. Generally you need to install to bare metal to troubleshoot wifi issues effectively.