A tidally locked planet does not rotate in relation to its sun. One side is always day, one, always night. This is caused by tidal forces pulling all planets towards this same equilibrium, so it’s completely stable once it does occur…a tidally locked planet at an earthlike distance from the sun would be scorching heat on one side, freezing ice on the other.
What about at different distances? Is there a band of orbital distance where the night side of a tidally locked planet is warm enough for liquid water? Or one far away enough that the day side can have oceans?
Temperatures would be okay in the twilight zone, not sure about water, but winds would blow you out of your shoes.
What about a planet so distant from its star that the day side gets as much light as earth at twilight? 2AU from a sol size star, there should be a quarter as much light during the day. What about there?
It’s worth noting that the human eye has a very wide range that it can adjust for brightness. Full daylight is 10000 lux, a room where visual tasks aren’t being performed can easily be 100 lux. 2500 lux would be very bright light in an indoor environment. From a societal perspective, this likely wouldn’t be enough to have an impact. From an ecological perspective, it could have a significant impact.
One thing that might also play a huge factor is the planet tilt compared to its host star, like Uranus’ spin. Or would that have a different name? Pole locked?