So yesterday Priceline followed up with Luxair again, and Luxair agreed to refund the taxes of $16.20. Priceline was also going to try to get the taxes from TAP.

This morning 03-Feb I had an unrelated flight out of LIS and noticed that Luxair was operating, so I figured I'd go a few minutes earlier to start an EU261 claim with them. Ticket counter was closed, check-in counter was open. I went to check-in counter, operated by a handling company. I asked for Luxair staff, was told they do not exist at LIS, it's all handled by the handling company. Asked for an EU261 claim form, they had never heard of it. Huh? So I asked for my passenger rights document, which they are required by law to have, they did not have and told me to go to the ticket counter, which they knew was closed. I stood my ground and demanded the passenger rights document or I would call the police to start a complaint for failure to disclose the passenger rights. They went to look for it in the back, and 40 minutes later produced the document, in Luxair letterhead in Portuguese and all. Per their instructions, to file a claim I will have to contact them in Luxembourg. Will do.