Found they do spawn on Astearos.

Time frame to try and tame them is 22:30-06:30 roughly

I have seen two per night so far.

I used extraordinary kibble but expecetional works as well.

*You don't have to do this but it worked for me*

I found one, shot it once with a shotgun for aggro. After it aggroed to me lining up the shot with the dragon claw to grapple was simple.

Once mounted it will show the moves it wants you to repeat. Follow moves exactly in the order given.

Next will be to travel distance. I simply just dived and got it done quick.

Last one is to do damage without taking any. ( They will spawn PTs and argys to attack you so watch out*) I recommend using the breath attack while flying backwards or away from the dinos chasing you.

Then jet feed it kibble.

Worse part right now is lag or DCing while attempting this.

Hope to update after further testing

*Foxhounds*