I'm shocked the SD card bit isn't first, and more surprised that the post doesn't suggest USB boot (I have one pi that's been on ~24/7 for years now, and I attribute its lack of problems to 1. using Alpine configured to barely touch disk, and 2. not having an SD card to corrupt - I don't know why USB would be more reliable, but anecdotally it is)
Yeah, exactly - as best as I can remember, and https://wiki.alpinelinux.org/wiki/Raspberry_Pi seems to agree, Alpine on the pi defaults to a mode where it mosly loads itself into a ram disk on boot and just stays there. Which means that you're constrained on "disk" space (your root filesystem is no larger than ram), but if your workload fits in that then you have the advantage that after boot the system pretty much doesn't touch disk.
I've had a bunch of Pi cards, running on SD without problems. But a single one suddenly developed a super-hot SD card, this was a brand new Pi which I was just setting up. Got the card out, and that one and the next Pi got a USB SSD and are now using those. That was a bit scary. But as mentioned I've also been running Pi with micro SD as Cups servers for years, with no problems at all.
Sample size of 1, but I ran an RPi4 just fine on a USB thumb drive for about a year.
Still upgraded to an SSD later because I wanted even more storage space (and SSD seemed to have better random IOPS than a thumb-drive), but I'd say go for it.
I don't really know. I assume they would be slower than SSDs though, but I have never measured USB flash. The SSBs get some 300MB/sec on my Pi 4 boards.
