Flashing Sailfish OS ‑ USB trouble

I got me a used XA2 Ultra (model no. H3213) that already had SFOS installed - albeit an old version, 3.0.something, so I wanted to reflash.

On Linux, this requires fastboot, part of android-tools on ArchLinux,and a script (provided with the image download) to do all that over a USB connection.

However, I kept running into problems - either I'd get a variety of error messages like 'GetVar Variable Not Found', or it would reboot into SFOS after any fastboot command, or it would simply hang at flashing the first image. Seemingly random.

Things to try ∆

Hunting for solutions, listed here in order - the last one finally helped:

• not a USB cable problem. MTP data transfers over SFOS work.
• possibly the "infamous USB3 problem" with a bunch of suggestions here. I tried everything, went into BIOS to disable devices on the same bus and ultimately set all USB ports to USB2
• possibly I need a lower version of android-tools - ArchLinux is on 34.something, SFOS suggests something lower. Installed locally, actually uninstalled the repo version. fastboot works, but the random symptoms persist.
• disabled USB Autosuspend with powertop as suggested here.
• disabled USB Autosuspend in TLP, which I am using on my laptop. Bingo!

Links ∆

Olf's Installation Guide, a great collection of timely notes on installing SFOS

Jolla's own Installation Instructions

Additional hints from a user

And of course the great community-powered Sailfish OS Documentation.