has anyone ever seen a gold tier 5 champion

Highest I have seen is a gold star level 4 personally.

I've gotten a level 3 Cho'Gath ONCE. I have never seen a t5 level 3.

i did not even see a golden epic [4cost] more then once.

tho the vid below show cased a tier 3 yasuo at min 9:00.

https://www.youtube.com/watch?v=zLv93Vqhqx4

I've gotten T3 Yasuo before...nearly had 2 T2 Yasuos and 2 T2 MFs in a recent match with my cousin that went for several rounds because his Shyvana wouldn't die at the end and would 1v7 until I finally beat it which made the match last forever.

Ive seen T3 Draven, Aurelion Sol, and Gnar. Nothing above that.

The only way you will see a gold t5 is if no one else picks em up and your rr rng is amazing.. there are only 10 of each t5 champs.. So you need 9 of the 10 to get that.. Probably won't happen. Considering the best chance you have to get a t5 champ is at lvl 9 (not much gold left after getting there) where you have a 10% chance to get a t5 champ.. While I'm sure it can be done, if you do it, buy a lottery ticket because it's your lucky day!! Attached the link w/ amounts of champs per tier, appear rates per lvl etc.

https://progameguides.com/teamfight-tactics/teamfight-tactics-tft-champions-list/

https://youtu.be/2j6QXTZXHwg?t=65 Ill leave this here... Yasuo 3* vs Reckful