Australia wants to force cats to stay inside or give them a curfew because they are murdering so many other animals they are a threat to the country's biodiversity
I'm one of those dickhead cat owners who seemingly can't keep their cat inside. We adopted our cat when he was 3 after spending a lot of time on the street, and ever since taking him in, he'd constantly howl to be let outside. We tried a few methods like an outdoor cat run, but nothing seemed to work.
We've got a GPS collar (and bell) on him and he seems to just stay super local, like within 100 metres of our house.
We've started to gradually transition him inside more but it's tough. We know it's a problem, but really need help getting him to accept inside life.
Growing up we always had outdoor cats and my first cat was outdoors and the more I learned that wasn't great I tried to transition inside after moving house, I figured it would work best alongside of change of scenery and like you described she just howled at the door constantly and stared out of the window.. I gave up after 6 months.
She is ok with being in at night though so at least there's that.
Have you tried a harness? Some cats that demand to be outside seem to be satiated with walks. Can take a while to normalize the harness with them, though.