I better check my sources. I thought Apple and Intel still had control over qualifying Thunderbolt 3 devices before sale to make sure they met compatibility.
Intel announced last year that they were going to release the Thunderbolt protocol under a nonexclusive, royalty-free license -
https://newsroom.intel.com/editorials/envision-world-thunderbolt-3-everywhere/ - but I have yet to see a press release announcing that it has been published and where developers can go to sign up. I do not trust Intel to follow through on this one at all. Not with AMD breathing down their neck, CPU-wise. They have 3 more months, so they aren't liars yet.
Intel was supposed to be at 10nm two years ago, now we're looking at Q3 or Q4 of 2019, so I will stick with 2020 at the absolute earliest for this to happen, if ever. Once I see it in the ARK -
https://ark.intel.com - I'll believe it happened.