Even if FLA were to play Knight in the AHL next season, it's just a matter of time before Knight lands in the NHL, likely by 22-23 season he's there to start the season. Thus, no point in him returning to FLA.
Sample size still limited, but we saw from 2015, the goalie movement that off-season with Talbot going to EDM, Lehner going to Buf, Lack going to CAR, and Jones going from LA to Bos to SJ, it doesn't always work out for the team taking a shot on a inexperienced goalie. Darling was a flop in CAR as well.
Teams that would consider him where he would get a shot at #1 job would be SEA, EDM, CHI, DET, TOR, BOS (though I think they would bring Rask back). The other teams have a goalie signed for decent money.
Freddie Andersen is the most experienced guy going to free agency who is likely to land as a starter. Dubnyk, Bernier unlikely to be considered #1. More of a veteran backup to a younger goalie as insurance.