Not sure how I dodged this! but I flew into Lisbon earlier in the week (via another European country) with a self-test. I did show my self-test certificate at the check-in desk and during boarding, then again as I was coming out of Lisbon Airport (just before you head towards the Metro station), they ALL checked my certificate and waved me on. They also checked it when I was checking in at the hotel.
When I left for Portugal, it wasn't stated that self-test were NOT accepted. If I went again, I would 100% get a test done with a on-site laboratory test company.
Otherwise, (In Lisbon) they ask to see your Covid pass when you visit restaurants/bars. Although some barely glanced before waving you on. The only exception is the Time Out Market Lisbon, where they actually scan your QR Code. On the Metro, everyone is masked up. There are various covid test centers throughout the city offering free tests (assume for locals) as I found all the websites in Portuguese (none in English).