I visited the palacio nacional de Mafra and its royal basilica and the adjacent park jardim do cerco on the 9th of oct.2024.

There are frequent buses between Lisboa's Campo Grande bus station and Mafra.

There are no toilets in the huge palace...there is a free one near the palace entrance.
The palace itself is large and tiring with its endless corridors and junk from bygone times...it felt like you were in a huge closet full of things that were simply put together in different rooms. Everything seemed disharmonious,...there was no consistent line...everything felt randomly arranged. Underwhelming world heritage site. The adjacent garden do Cerco with its aviaries was also relatively unimportant. The basilica is mildly interesting. I like palaces,but this one was surprisingly boring and underwhelming. 

Just one recomendation: try to visit the Queluz palace in Lisboa's outskirts........fantastic....one of the most beautiful ones I have seen in my life. Mafra cant hold a candle to Queluz IMO.