My favorites are the couch stretch and the basic low back mobilization right after a run (both can be found here – https://thereadystate.com/pain-injury/lumbar-spine#popup-67757). I find that after a long run I don’t want to do anything too harsh. I keep the couch stretch super easy and gently relax into it and then enjoy being on the floor for the low back mob. When I finish the low back mob, I will do legs up the wall and just relax for a few minutes to let my body down regulate. Later in the day when I’ve recovered a bit and my muscles are not so exhausted, I will do some rolling on my feet and maybe some quad smash and elevated pigeon. I will also repeat the couch stretch.