I didn't get you. Tablets allow only to split screen (except for some launchers that allow a kind of tiling with multiple apps) while Chromebooks allow standard windows like any X/wayland DE, plus they allow tiling similar to tablets.
I have to test but I bet with other operators it would stay 4g until you receive or do a phone call.
That's how it works a 4g huawei I got.
It takes some time to switch between 4g and 2g but it works
Like "standard phone calls have always been interoperable" ?
Like "batteries should be replaceable" ?
Or "documents file formats should be open" ?
ActivityPub should probably become a login standard, somehow as standard as SAML.
Any social network should propose to login with AP, just like any social let you use email or phone number to register.
Tumblr said that too but never did it actually. It's not so easy to join a network where the skills of any single "kid" could be compared to your 1000+ employees company.
It has artemis which is alpha but actually it's a sweet app.