The Senegalese defender was involved in a horrific road traffic accident on the M4 in 2016 which saw him airlifted to hospital.
He has only played 25 games since that day and was with French side Troyes last season, having left the Eagles in 2019.
But he has been back training with Palace's Under-23s since the start of pre-season to maintain fitness and aid his search for a new home.
An Eagles statement added: “It has been a mutually beneficial arrangement, as Souare's presence has provided an extremely positive experience for the club's younger players."
Souare, 31, made 63 appearances for Palace across all competitions after moving from Lille in 2015.
Need a VPN? Or seeking to switch? Then support Tribal Football by clicking here to sign up with our official partners NordVPN. Not only will you receive the best VPN experience, but also great discounts by signing up via Tribal Football. Thanks for your support!