Starting a PhD without wanting an academic career afterwards: should I tell my advisor?
This is pure opinion, of course, but I don't see anything wrong with getting a doctorate purely for the love of the field and a desire to know more. There are plenty of people in doctoral programs to fill the needs of academia in the future and some will be disappointed in their inability to find a suitable position. You don't need to apologize for anything.
But you may be a bit naive about the future and your ability to make a living. If you really aren't concerned about that, then there shouldn't be any problem, but understand that you may not find any position in which your new knowledge can be leveraged. But, there are other opportunities outside academia and industry if you have the financial resources to manage it.
Whether you talk about this with your advisor or not is a personal decision, and should be based on your understanding of how they might react. No one here can predict that better than yourself.
But you really aren't deceiving anyone. As you say, your future is yours to manage.

Back in the day, previous century, actually, we didn't worry about what came &quot;after&quot; since the economy was good and there was a lot of interest, both in academia and elsewhere in our skills (math, in my case). We were just able to assume that jobs would be there. But all of that ended when we successfully landed on the moon. So it was a shock to graduate into a terrible economy for folks with doctorates. But now the situation is very different. There is an abundance, not a lack, of skilled people, so the future is much less &quot;certain&quot; now than it seemed to be in the 1970's. Make sure you have plans, and back-up plans as well.