For me the golden rule here is "how do my actions affect trans kids?" (And adults too for that matter).

For most people, playing a HP video game will make HP content more recent in their brains and come up more in their thoughts and conversations.

For a lot of people, knowing what the author supports makes HP less fun... just like Ender's Game before it, and countless other properties.

It makes sense that a loss of a cherished story from childhood is felt as a loss, and the books and related media were important to a lot of us growing up. There might be some contexts where talking about HP doesn't increase the demand for it, or enrich JKR, like if you're criticizing it or talking about how you don't like it any more, etc.

If someone theoretically never knew anything about JKR and never told anybody about HP, then theoretically them enjoying the stories would have no effect on anything. If someone is in that boat, awesome. Keep living your best life, theoretical HP-enjoyer who doesn't discuss it!