The idea is good but does not work I made 3 connections with screenshot to confirm. With VPN │Without VPN │Incognito
My fingerprint always remains the same and the technical demo knows if I am in private mode. I invite you tried.
♦ https://fingerprintjs.com/demo/
I'll contact the developer to see what he thinks!

Unfortunately the addon doesn't seem to work in the latest version of FF (67.0.4 64-Bit), the canvas fingerprint attempt gets detected, however the reported values always stay the same. I've used browserleaks and one more website for testing but result stays the same.

P.S. I wasn't able to submit a bugreport on your website, it throws an error each time.

I love this Firefox addon, the reason I gave 3 stars its because it will always show your fringerprint in the first session, if you refresh, them it will change it, but the first one, it will always show your real one.
But, well done! I am considering donating to see if they can fix this issue.