Universal clipboard is pretty great too. It's another thing I wish was just an open standard that all the things supported, not just the Apple ecosystem.
I get a lot usage out of related cousin feature Universal Control, which is the best KB/mouse sharing implementation I’ve used. It manages to feel almost identical to a physical connection even over WiFi, which nothing third party has been able to swing… Synergy, Sharemouse, etc need all involved machines to be connected to the network via Ethernet to pull that off.
Interestingly, it seems to present shared KBs and mice as physically connected devices. Any time I use Universal Control on a Mac I haven’t before the little keyboard identification assistant that opens when you directly plug in a keyboard pops up.
I'd never reflected on the irony of these features being called Universal when they only work on Apple devices, but the 'just works' nature really does feel good.
I sometimes need to work on mobile development, so on advice from a sibling comment I installed KDE Connect, and it's actually pretty great and does copy/paste and remote mouse/keyboard pretty well, but you do have to a) enter the app, b) select the device, c) then finally choose the thing you want to do. They've made it about as frictionless as possible, but it won't be the same as first-class OS-level support. e.g., I can just copy some text on my Mac, and paste it a second later on my iPhone, without any manual orchestration
I hadn’t encountered KDE Connect before, I might check that out for MacOS to Android. It looks like they’ve done the best they can on iOS, I’m spite of how locked down it is
There could be a standard protocol describing how to authenticate and talk to a server, and get notified. It's not that different from chat protocols.
And operating systems could allow user to select their preferred server, although I wouldn't expect Apple to allow something advanced and anti-vendor-locking like that.
