"The sovereign grant was increased in 2017, from its previous level of 15%, to pay for extensive renovations at Buckingham Palace which are likely to run until 2027."

And Buckingham is part of the Crown Estate, which is not the private property of the monarch.

No, Buckingham Palace and other “occupied” royal palaces are not part of the Crown Estate.

”The palace, like Windsor Castle, is owned by the reigning monarch in right of the Crown. Occupied royal palaces are not part of the Crown Estate, but nor are they the monarch's personal property, unlike Sandringham House and Balmoral Castle.”

Did some research; think I’ve figured it out. See whether this is correct.

Occupied palaces, like Buckingham Palace, are owned by the reigning monarch ‘in right of the Crown’ (like you pointed out).

Similarly, the Crown Estate belongs to the reigning monarch ‘in right of The Crown’.

“In right of The Crown” means it is owned by the monarch for the duration of their reign, by virtue of their accession to the throne.

So, you are correct (and I was wrong) that Buckingham is not part of the Crown Estate.

Notwithstanding this technicality, would you agree that the overarching point remains that it isn’t as if “the money goes to the monarch for their personal enjoyment” (which is what I interpreted you implied), but towards Buckingham renovations, which is a property of The Crown[1] (i.e the state) and which in turn is embodied by the reigning monarch.

It sounds to me as if the monarch is like a custodian/shepherd of these assets for the benefit of the state (the crown).

[1] https://en.wikipedia.org/wiki/The_Crown