The State Street, Market Square, and Dwight Kessler garages are all free during home games. Also, street parking on Gay and many of the surrounding spaces are pay, but a 2 hour limit, so they turn over easily and aren't occupied by folks attending the game. See https://www.downtownknoxville.org/explore/parking/?t[]=37
There's paid parking everywhere. It gets cheaper the further you're willing to walk, and if you don't mind being blocked in.
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