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Windows 7, 8 and 8.1 support will end tomorrow (January 1st 2024)
(help.steampowered.com)
Steam is a video game digital distribution service by Valve.
Steam News | Steam Beta Client news
Useful tools:
SteamDB
SteamCharts
Issue tracker for Linux version of Steam
I would go for Zorin! It's based on ubuntu and quite close to the windows experience so easy for beginners!