It's possible but wouldn't recommend at all due to drivers and cut support.
I'd recommend Windows 10 LTSC instead, as it still has support right now and is basically just as lightweight as the final Windows 8.1 build.
Either way, you can get them both versions from 
Bob Pony's Microsoft Archive from the front index of this forum
	
	
		
			
				
			
			
				
				Download from our massive collection with ease.
				
					
						
							 
						
					
					bobpony.com
				
 
			 
		 
	 
Put on a USB by either Rufus (Single ISO) or Ventoy (Multiple ISOs on one USB)
	
	
		
			
			
				
				Rufus is a small application that creates bootable USB drives, which can then be used to install or run Microsoft Windows, Linux or DOS. In just a few minutes, and with very few clicks, Rufus can help you run a new Operating System on your computer...
				
					
						
					
					rufus.ie
				
			 
		 
	 
Activate via massgrave:
	
	
		
			
				
			
			
				
				Open-source Windows and Office activator featuring HWID, Ohook, TSforge, KMS38, and Online KMS activation methods, along with advanced troubleshooting. - massgravel/Microsoft-Activation-Scripts
				
					
						
							 
						
					
					github.com
				
 
			 
		 
	 
(Click Code>Download ZIP>Extract>navigate to "MAS\Separate Files Version\Separate-Files-Version\Activators\HWID_Activation.cmd)
And for drivers, laziest quickest method is Snappy Driver Installer Origin then do Windows Updates:
	
Good luck!