EDIT: The day after I released the video, Spitfire redid their entire website. The links still work, but it will look a little different.
Hey, so since it took me so long to figure out how to get Spitfire working in Ardour on Linux. And after I was asked to upload a tutorial, here it is. :)
Hope you find it useful, if you have any questions I hope I can help, though I'm much more a musician than a technician...
Feel free to comment about your thoughts, and if I missed anything, I am very new to Linux and would love to correct any mistakes.
Links:
Plugin installer - https://www.spitfireaudio.com/info/library-manager/
Unfa / great Ardour and linux audio tutorials - 
Spitfire labs YT channel - https://www.youtube.com/c/LABS_IIO
check them out and give them a like and subscribe, after all, we wouldn't be here without them.
▶️ 3Speak