"fits in a backpack", with the implication that it will consume the internal volume of said backpack. That does not make it a solution for parent's "backpacking trip", unless you wish to sleep on the ground in the clothes you wore. And you ate before your left. The "heavy battery" was just icing on the cake. You know some backpackers saw the handles of their toothbrush to impress other backpackers^W^W^Wsave weight, right? :-)
That's not to say Starlink or a competitor can't get there eventually. I already have pocketable/backpackable device that can shove data up and down a satellite link (Garmin InReach), it's just dog-slow, and that's likely down to the antenna and transmitter power if I were to guess. Someone with more RF smarts than I can probably cook up a foldable antenna, perhaps boost the power a bit, I dunno. But the PoC is there, it just needs iteration.
This is more of a physics problem than an engineering problem.
Garmin InReach uses an omnidirectional antenna on the Iridium network. With an omni antenna your S/N ratio is simply too low to send bits fast. If you made the device powerful enough to roast birds in flight it might work for faster uplink but then it would be dangerous to you too and the FCC would never let you use it anyway. And even this wouldn't improve your downlink speed.
The only way to improve the speed in both directions is to use a directional antenna, which points most of the uplink energy toward the satellite and concentrates the satellite's incoming energy to get the S/N ratio high in both directions. That's exactly what Starlink does.
This is made even more difficult because we're talking about LEO satellites and LEO satellites move. So the antenna has to track the satellite. Again this is what Starlink is doing.
(You can also use GEO satellites which don't move, but then latency becomes terrible. That's how the older satellite internet systems work.)
It's certainly possible to build a portable, directional, tracking LEO satellite antenna. That's exactly what the Starlink RV solution is. But it's never going to be as small as your Garmin unit.
