I wrote to the Albergue De Peregrinos Armenteira (municipal) about two weeks ago inquiring about reservation, and didn't hear back from them. I wonder if this implied dispute with the local government is why. Per this
thread from 2023 and the
Albergues del Camino de Santiago website, they did indeed take reservations, though it was a recent change in the last few years. (That is, Camino Chrissy's recollection that they did not take reservations in 2019 would be correct, but they changed to taking reservations in the last few years).
You are correct about the Armenteira Monastery, they no longer take reservations
per their website here. I had written to the Monastery earlier this winter and Hermana Paula kindly let me know that indeed they will still take pilgrims, but only on a first-come, first-serve basis.
Because I'm much too anxious, I booked at
Carballo de Prado 1900 which has really good reviews. Should be 75 euros for two people, one room. They offer free pickup from Armenteira Monastery starting from 4pm, and I believe will also deliver you back to the Monastery the next day.