Conditioning is a little different for me now. I definitely don't get to bogged down in rest time vs. on time. When everything is correct I'm training 6 days a week so I don't go as hard on a conditioning session as opposed to if I was only doing 4-5 sessions.
I will usually try to pre-exhaust on a set of squats before the conditioning with a focus on a squat pattern I didn't hit the day before.
Hill sprints mainly, it's a sizable hill so the initial incline requires that that glute/ham activation and the top end gets the cardio if that makes sense. Usually 10-12 of those get's my hams right on the edge of a tweak and I end it there. I will usually walk down the hill at a decent pace and then go right back up.
If I do flat sprints it's 20-30 yards more focused on burst/explosion. I really only have access to pavement so all that pounding on my joints is no bueno. I usually will pair those will a longer run that's closer to 100 yards at 80%
My real go to is the prowler super-set with loaded carries. It's right around a 40 round push with intermediate weight down to one end, walk back with to KB to the other then walk back to the prowler and repeat. I don't rest between the prowler/carry transition but usually 12-16 deep breaths after the carry on the walk back. I do whose in sets of 6-8 so one full trip down and back with the prowler and the KBs is a set. The other variation is lighter weight with a down back non-stop and then carry the KB's. You get upper, lower and core with this combo

I tried the treadmill flat and that danger just wasn't worth it as a regular thing. Also I was more prone to pull something

. I wouldn't be against the incline, it just so happens there is a paved longer hill right behind my gym.