After the firing of Clayne Crawford (I remembered his name this time without having to Google it), it looks like Sean William Scott is the casting replacement in Lethal Weapon.
Scott will not be playing Martin Riggs. According to Deadline:
In his first series regular role, Scott will play a new character who will be partnered with Wayans’ Murtaugh. The recent Season 2 finale of Lethal Weapon laid the groundwork for Crawford’s exit with a cliffhanger.
Deadline also claims that Scott may play the brother of Martin Riggs. Which sounds a bit weird. One thing is for sure, Crawford must be some kind of asshole to force the studio’s hand to make such an awkward alteration.