I talked to a therapist about this once and he told me to volunteer or have kids. Haven't talked to a therapist again since those were dumb suggestions.
Settled into just enjoying my life and building for the future. Work out, have a dog, have a partner, build cool things. No more existential dread about purpose.
From my experience, volunteering directly helping people has been highly rewarding.
Ideally, find somewhere you can volunteer the specific skills or interests you have to help people who otherwise wouldn't benefit from what you can bring to the table.
Ideally, it would also be physically active and interfacing directly with others in some way. (And not too closely related to what you do for your day job.)
Settled into just enjoying my life and building for the future. Work out, have a dog, have a partner, build cool things. No more existential dread about purpose.