Don’t recast Chekov and don’t kill him.
Have the character have transferred to a different ship and be doing just fine. He sends Sulu messages about how he’s doing. Then respect why Chekov was originally there and make the new person in his seat an Iranian, Iraqi, Syrian, or Saudi Arabian woman. Chekov was there to predict a future where the Russians, America’s greatest enemies at the time of the shows creation, were our friends and allies. Pay respect to why he was created by placing a Muslim woman from a country that America has warred with in the seat. Give her a gold dress, black long sleeve undershirt, black leggings, and a federation uniform approved hijab. The movies would be creating representation and paying respects to what Chekov was there for. Put a muslim woman in the navigators chair and let her fly us through the stars.