I didn't keep track of WebOS after I left Palm when it was acquired by HP. AFAIK there were some OG people still on it and some of the stack was still the same. I met one of the people at a Palm reunion many years later and he was complaining that PBNJSON was still in use. This was a significantly better / faster / more secure C++ JSON library I wrote (both had better test coverage and things like formal schema validation which wasn't a thing at that time for JSON). It was severely delayed in getting open-sourced and then it seems like no one really is invested in updating this part of WebOS, otherwise they would have replaced it with RapidJSON or even better Rust Serde or something like it.
As I said, today it's fine and AFAIK it's also on car infotaintment systems (the ARM ecosystem is way more mature with respect to web / JIT + much better supporting ecosystem). It's less clear to me if they still use a normal Linux ARM kernel or if they've switched to Android. The biggest problem with us not using Android is that Android sucked up all the oxygen and device vendors built Android instead of Linux drivers / provided binary blobs that only worked on Android. This increased costs because those drivers needed to be ported to normal Linux.
However, most (all?) of the really talented designers that pioneered WebOS got snapped up by Google and Apple. So did a lot of senior engineering talent (probably moreso by Google since a lot of them were already ex-Apple and not keen to return).