How do you get the Season 2020 - Flex Silver Icon?
It was a ranked reward. Riot's description in the client reads: “This icon was earned by finishing Silver in Flex Queue in Season 2020”
Is the Season 2020 - Flex Silver Icon still available?
No. The Season 2020 - Flex Silver Icon was a ranked reward. To earn it, you had to reach Silver in Flex during Season 10 (2020). Riot does not hand out past ranked rewards again, so you cannot earn this icon anymore.
