I’ve just reported it via the EUCARE app, so I may as well come clean now – Andreas is actually me. The app worked alright, or at least well enough for me to fumble my way through. The video consultation just lasted 7–8 minutes, with the doctor wanting to see my NHI card and the positive test result and asking if I had any symptoms. He said he’d send some messages and medicines* (not sure how), and that I’d later receive a quarantine order dated to yesterday.
Feeling it a bit more today. It’s impressive how quickly/easily it spread on Saturday – the friend who tested positive on Sunday apparently gave it to three of us (that we know of), including one guy who barely spoke to her and was mostly outside. The only ones who didn’t get sick this week were those who’d already had it in the last couple of months, including her husband and the wife of the above-mentioned guy. I think everyone has had three vaccine shots. I assume more people we didn’t know in the bar will have caught it as well, because it’s quite a small place and it was pretty crowded for a concert.
(*Yeah, I’ve received a prescription in the app for 5 different drugs, in typical Taiwanese style. No idea how I’m supposed to fill it, but might not take them anyway. 
)