Earlier quoted context omitted.
Look up CloudKit[1], many of these questions have been answered for Apple-native apps, but perhaps it's not obvious how to translate that to the web-world, or how to keep the object storage decentralised (but self-hosted shouldn't be a problem). I'm also firmly in the native app camp. And again, Apple did this right. The web interface to iCloud works great from both Firefox and Chromium, even on OpenBSD, even with E2…
> I'm also firmly in the native app camp. Then you are answering the wrong question. I want a "web native" answer and proposed a simple modification of existing Web APIs. As a mixed iOS/Windows/Linux user, I have selfish reasons to want a cross-device solution that works at the Firefox standardized level. Even outside of the selfish reason, the kinds of "apps" I've been building that could use simple device-to-device…
I don't see why this mechanism shouldn't be available both on the web and in native apps. The libraries would just implement the same protocol spec, use equivalent APIs. Just like with WebRTC, RSS, iCal, etc. And again, ideally with P2P capability.
> [...] that works at the Firefox standardized level.
What about a W3C standard? Chrome hijacked the process by implementing whatever-the-hell they like and forcing it upon Firefox & Safari through sheer market share. It would be good to reinforce the idea that vendor-specific "standards" are a no-no.
It also just doesn't work the other way: Firefox tried the same thing with DNT, nobody respected it.
> Piggybacking on Passkey roaming standards may be a possibility here [...]
WebAuthn sounds good, that kinda covers the TPM/SEP requirement. Native apps already normalised using webviews for auth. I wonder if there's a reasonable way to cover headless devices as well, but self-hosted/P2P apps like Syncthing also usually have a web UI.
> [...] again selfishly at least.
No problem with being "selfish". Every solution should start with answering a need.