Edit: I'm now enlightened and use mpv, I really like the ModernZ OSC (on-screen controls), and uses config files.
IINA is only on macOS. I looked up linux alternatives but none of them seem to have similar looking UIs, at least out of the box. I want the player UI to float on top of the video + with a blurred background, it as shown in the image; or at least the ability to theme it like so.___
Doesn't IINA just use the native macOS video player interface? (I mean, I know it has a lot more on the hood, but that picture just shows the native video player interface.)
So I'm thinking a VLC skin might get you at least partway there?
Mac user here, and I use VLC. Sometimes it uses the native interface, sometimes it uses the VLC one. I'm not sure why, or how it chooses. macOS is kinda janky like that. I'm also relatively new to the platform.