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