A Darth Maul Leg Synopsis
After Obi-Wan cut him in half, Maul managed to find his way to a trash compactor, where the Star Wars Databank indicates he was dropped off on the junk planet Loto Minor, where his brother Savage Opress discovered that Maul, mad and living on rodents,
had built hideous spider-like legs in place of his severed ones.
Savage Opress returned with Maul, Talzin then replaced his legs with the raptor-like legs you spoke of, made from the remains of Separtist droids, as shown in Star Wars Clone Wars episode "Revenge". He later loses one of these legs (and Opress loses his arm) during a battle with Kenobi and Adi Gallia in the Clone Wars episode "Revival".
In their escape from Kenobi, Opress and Maul were then rescued (they had run out of oxygen) by the Death Watch, who took them to the planet Zanbar.
On Zanbar, medical droids healed Maul from his wounds and replaced the
legs he had received from Mother Talzin for a pair of Human mechanical
legs that returned him to his previous height.
This is shown in the Clone Wars episode "Eminence".
At no point could I find a reference to him getting new organic legs, however it appears that in the time between Clone Wars and Rebels, he did get an upgrade of new, even sleeker legs - though this could merely be due to the art shift between series.
Note that these legs have the same patellar plate as the legs Maul used when he tried to fight Sidious with Opress.
Moreover, these legs
appear to be the same ones he wears in the Solo movie.