How do you get the Season 2019 - TT Platinum Icon?
It was a ranked reward. Riot's description in the client reads: “This icon was earned by finishing Platinum in Twisted Treeline in Season 2019.”
Is the Season 2019 - TT Platinum Icon still available?
No. The Season 2019 - TT Platinum Icon was a ranked reward: to get it you had to reach Platinum in Twisted Treeline 3v3 during Season 9 (2019). Riot does not give out past ranked rewards again, so it cannot be earned anymore.
