Early morning here also due to family/work. If it’s a shorter workout and I need to sleep in because of working late I do it over lunch. During the summer I really love mornings because it’s cooler and less humid (my pain cave is in the garage). During the winter it sucks but builds character!
One problem with mornings is as mentioned above warming the legs for intensity. If you feel extra stiff you can always extend the warmup before getting into it. Dynamic stretches also help, and coffee of course.
I also find that fueling can be an issue for the really intense efforts and the first few intervals can feel pretty flat. So on bike nutrition is very important if you’re riding early. Also you have to make sure you are in bed early enough or you will sell yourself short due to lack of sleep. I have a strict lights out at 9:30 policy and am up no problem at 4:30 to start my morning with TR.