Given how Frieza was able to do Image Training while in Hell...

[Steven Bloodriver]

Would he have eventually been able to escape on his own if he had not been recruited for the Tournament of Power of the Dragon Ball Super Anime? With I guess Android 21 or Broly: BR replacing him for the tenth member of the Universe 7 Team and leading to one of the two being the one to have defeated Jiren.

As I believe Android 21 is by far more intelligent than Jiren and would find out a way to defeat him, probably by playing on the fact that he might underestimate her just a little too much for his own good because of her Base Form having such an ordinary-looking appearance. While Broly: BR would have a much easier time against Jiren since the Legendary Saiyan of Universe 7 would take him out in his Legendary Super Saiyan form.

[Lionel]

I don't believe it works like that. If an individual's final spiritual resting place were escapable then you would have everyone stronger than Yemma easily breaking free and running amok in the afterlife. Somehow the mechanics of judgement and condemnation operate differently. If it were as simple as power overcoming his imprisonment in hell then why doesn't Freeza use his Kosengan or Kiaigan to decimate the trite frilly little caricatures tormenting him? His face isn't obstructed or hindered. My only guess is that his entire body and ki was immobilised somehow. Perhaps it follows the same mechanics as the ofuda that ensures the creature or person trapped in the Mafuba container can't escape on their own.

[MKCSTEALTH]

Given what little we know of Toriyama's version of Hell, I'm going to say it would be unlikely. I feel Frieza would've been trapped until he was either resurrected again or...repented or whatever is supposed to happen next