The trajectory of the last French air carriers - the Foch and the Clémenceau - is a good illustration of the mess it can be, even for former military flagships.
Those military ships are of course full of asbestos - more than usual - and heavy metals.
The Clémenceau was supposed to be dismantled in Spain, but when the marine nationale saw it being towed to Turkey, they cancelled the contract and got it back.
Then another consortium offered to dismantle it in Alang but with special precautions. The boat left, was blocked by NGOs, was blocked by Egypt when it tried to cross Suez, then India refused to accept it. It came back to France after rounding all of Africa.
It was eventually dismantled in the UK, after a few more protests (the river Tess had to be deepened, and the hull had to be cleaned up of any invasive organism)
https://fr.m.wikipedia.org/wiki/D%C3%A9mant%C3%A8lement_du_p...
The Foch was sold to Brazil, and after much of the same drama, was eventually sunk in the Atlantic.