There’s no new information here. I’m merely illustrating techniques that others have described in this and other threads. Partly this is in response to questions by @Hilary
in a different post.
First I used a oscillating tool with a knife blade (Not a saw blade!) to separate the joint from the inside. I used a snap-off utility knife with the blade extended to cut at the corners. You could also do this with the rest of the frame, but it would be a lot of work.
Then I used a flexible putty knife with a hammer and went all the way around the exterior frames.
After that, the portlights came out fairly easy. I very gently used a prybar. Aluminum frames are easy to bend. As with with other posters here, some of the original caulk was still flexible and other parts had deteriorated to a dry putty. This leads me to think it was something besides silicone between frame and cabin wall.