They're mostly just using FFmpeg behind the scenes, which is exactly how Plex did it to start with. Plex spent a long time working on hardware acceleration, it's hard to tell exactly what they're doing at this point but it's safe to say they spend a hell of a lot of time on it so I doubt they're just using FFmpeg for hardware acceleration anymore.
They're mostly just using FFmpeg behind the scenes, which is exactly how Plex did it to start with. Plex spent a long time working on hardware acceleration, it's hard to tell exactly what they're doing at this point but it's safe to say they spend a hell of a lot of time on it so I doubt they're just using FFmpeg for hardware acceleration anymore.
Hilarious if they are, they'd just be getting people to pay to use their own hardware
I mean it's not entirely impossible, FFmpeg has also pushed to improve themselves over the years.