Fuchsia has a crap load of wild ideas. Microkernel, capabilities, weird app installation system (I think they're trying to make apps more like websites).

https://rtic.rs/ is a pretty cool idea for an embedded RTOS (sort of).

Honestly though there's still stuff in Plan 9 that is way more advanced than what Linux does, e.g. https://9p.io/sys/doc/lexnames.html