Ah, got it. I was confused because Aleph has been a thing for a very long time. I didn’t click that it was “…on Steam” that’s the important part.
I loved Marathon back in the day; played the hell out of it on an LC475, and it was a key reason why a) I stuck with Macs in my post-Amiga era, b) made me a fan of Bungie in general, c) broke my heart when Halo became an XBox exclusive, and c) resulted in my buying an XBox anyway because Halo is/was basically Marathon 4.