I gotta imagine it's like 99% Steam these days.
My impression is that very few people today are aware that buying from Steam isn't just a lot less money for FDev for the purchase, but also forever slashes how much money FDev gets from any later DLC, expansion, and cosmetic purchases, regardless of whether you try to buy them directly or not. The game account is forever associated with Steam and so even purchases directly from FDev must still pay the Steam tax.
For anyone coming into the game, I suspect it's often not even obvious there is a non-steam way to buy it. Let alone that there is reason to not get it on steam. You heard of a game that sounds good? Look it up on Steam. Add to cart or to wishlist. Why would you search further? Even if you do search further, it's probably gonna be for YouTube videos.
I think these forums give an illusion of more direct sales because a lot of the activity here is from old-timers, but that's just several hundred people, statistically nothing.
[Though quite a few of those old-timers who are still active, will be "whales"]
I think that has to be balanced by more old timers tending to stick around and continue to play vs people who grabbed ED on sale via Steam, played it for 50 hours, got an Anaconda, then quit.