Yep, Avernus is the first layer of the nine hells . And it is where much of the of Blood War takes place.
I'm running Descent into Avernus for my players, which is apparently the prelude to Baldur's Gate III. In it, players go to Avernus as early as 5th or 6th level. And also in Avernus there are numerous low level NPC civilians hiding out trying to survive until the heroes can rescue them.
So low level people can survive in hell. If only by the skin of their teeth.