Sorry for the super late reply, it's been a while since I checked here.
I don't remember the specifics now, but one stage I DO remember is the Speed Highway stage in 2022's OLDC pack, round 2 I think.
It gives you a solid 3 minutes, and Speed Highway has a decent amount of enemies: but it's a BIG level. The enemies aren't as helpful, because yes, there are a few of them - but they're very thinly spaced out. Not ideal for combos. The entire last section of the map only has a measly cluster of four enemies in total, as an example, so you can't really rely on combos to keep the clock at bay.
I'm no speedrunner, so I don't really know any of the techniques I could use to theoretically snap the map in half (I'm sure there are some), I just follow the main routes. I had another friend who tried, too - neither of us could beat Speed Highway in a single life.
That's my only example, though. Other levels do mostly work fine, Gamma does pretty well in Sol Sestancia, and I'll probably try Cyberdime at some point.