score:2
Unfortunately this is a prime example of Covid paperwork madness. You can't check in without the PLF (passenger locator form) and you can't file the PLF without having a seat, so you have to check in first.
If you can't get a seat online upfront, you have a bunch of options
We flew to Portugal about 3 weeks ago and check in was a disaster. Huge line at the check-in counter moving extremely slowly and another huge line at the gate for document verification (for those people who managed to check in online). As a result the flight left over an hour late.
TIP: the PFL confirmation you get by e-mail is password protected PDF, but they don't tell you what the password is. Turns out, it's your passport number. It's incredibly inconvenient to have to pull out your passport and type in the number every time someone wants to see the PFL. You can remove the password simply by printing it into a new PDF file.
The whole experience was a total mess.