It would be quite different from Earth in lots of ways. The most habitable region would probably be the twilight zone but “life will find a way” as Jeff Goldbl

It would be quite different from Earth in lots of ways. The most habitable region would probably be the twilight zone but “life will find a way” as Jeff Goldblum famously said. Life would have been evolving for billions of years in that environment before intelligence arose. The temperature gradient might not be as nuts as you’d think. A thick atmosphere would develop powerful prevailing currents that would move heat from the hot side to the cold one, basically a heat engine. It would keep the hot side from being insane and the cold side from being cryogenic. My guess is that the far poles would be extreme but anywhere from 1/3 to 2/3 of the non-twilight sides would be potentially habitable by something. If there were large oceans you'd get prevailing currents there that would move heat too. There’d also be a water cycle. Imagine regions of the hot side where it rains a lot. You might have this hot steamy jungle in eternal daylight, meaning 2X the energy available for photosynthesis. There’d probably be critters that would migrate around. I can imagine stuff living on the night side by eating those, scavenging, etc. I wonder if an environment with massive prevailing winds would drive the evolution of wind energy harvesting? Imagine a big tree like thing with big leaves or vanes shaped to flap in the wind and specialized cells that use that mechanical energy to make food and nutrients. Muscles go from sugars to motion. Seems plausible that something could go the other way, especially with billions of years of evolution and a massive amount of energy available that way. If that kind of thing evolved you could have wind powered ecosystems on the night side and solar powered ones on the day side. Lots of possibilities.