It is not an uncommon practice for coaches to send letters out to returning Sr./ 5th year Sr. players who have not seen a lot of playing time, low on the depth chart, saying something to the effect "you are welcome to report to camp, but we will be giving younger players at your position more reps ...a closer look...I better chance to advance" or something like that. The newer the coach, the more likely these letters are sent out to players they did not recruit. A tough message, but fair and honest.
That said, young players, perhaps 2s and lower, with little success in establishing themselves as starters, 2 or 3 years left, especially on teams with new coaches, seem to be the best options in the portal. Iowa has had good luck with a couple of transfer O-Linemen and D-linemen recently. Younger All-Conference MAC players, Big 12 players ll seem like fertile ground. Especially, players who we had recruited, and offered but lost to other schools. An exciting time, with second chances all around.