How do you get the Season 2023 - Split 1 - Flex Challenger Icon?
It was a ranked reward. Riot's description in the client reads: “This icon was earned by finishing Challenger in Flex Queue in Season 2023.”
Is the Season 2023 - Split 1 - Flex Challenger Icon still available?
No. The Season 2023 - Split 1 - Flex Challenger Icon was a ranked reward. To earn it, you had to reach Challenger in Flex during Season 13 (2023). Riot does not hand out past ranked rewards again, so you cannot earn this icon anymore.
Season 2023 - Split 1 - Flex Challenger Icon is one of the rarest LoL summoner icons.
Released in 2023

Season 2023 - Split 1 - Flex Grandmaster Icon
Released in 2023

Dunkmaster Darius Mythic Chroma Icon
Released in 2023

Season 2023 - Split 1 - Flex Master Icon
Released in 2023

Prestige Edition Soul Fighter Pyke Icon
Released in 2023

Season 2023 - Split 1 - Flex Diamond Icon
Released in 2023

Soul Fighter Gaze Icon
Released in 2023
