Whoo hooo! I'm the first to write a tip on encountering!
It's only found during heat waves on scorched, probably just spawns anytime on modded maps in a few days.

The Phoenix eats sulfur only sulfur and nothing but sulfur so just keeput that in mind after you tame one.

Only one wild Phoenix will spawn at a time per map.

It usually spawns near the red obolisk or the sand dunes or the Rocky mountains behind the red obolisk. 80% of the times it's their 15% of the time it's near the silicon pearl loop in the middle of the map 5% of the time near the corners of the map. Happy hunting.

After heat wave is over where the Phoenix went into ashes next it heat wave it’ll spawn there! -TBFlame

Follow it then let it dissipear waiting for the next heat wave. Then trap the ashes/where it temporarily died, and start flaming it with flame arrows, a fire wyvern, or torches.

Use s+ tek transmiter. Use dino scan in this item.
U see 3 phoenixes on each map.

Only 1 phoenix per map is wrong.

Can use fire wyvren insted of arrows.

Ha. Good luck finding it. Nearly impossible