Yes, both the Ally and the Go are sold in Australia. However it’s also quite easy to order a “grey import” Steam Deck from Amazon, which is what I did. I’m guessing the sheer number of Steam Decks that have been sold into Australia that way are factoring into Valve’s decision, because anecdotally among my peers the Steam Decks owned outnumber the Allys 4:1. Pretty impressive for a device not officially sold here.
I’ve had two different arch based distros have issues when trying to update after long periods. I also had an Ubuntu server fail completely when doing a major version upgrade and had to restore it from backup. But then again I’ve also had no trouble updating an Ubuntu machine that was a couple years behind.
I’m on Fedora now for my desktop and it’s been great so far, but I also do updates at least weekly. My advice would be if you expect to go months between updates your best choice is probably Debian.