Used Novo Banco ATMs in Porto and Lisbon with my Revolut card-no fees were charged.
On our Algarve trip, we used Irish debit cards at Caixa Geral. No fees at all-we double-checked the receipt!
Caixa Geral ATMs were only available in bigger cities. Worked well with our foreign debit cards and were very clean.
During my 1-month trip through Portugal, I kept using Santander with my Sparkasse debit card. Always reliable, never had any problems.
Used Santander ATMs multiple times while traveling from the US. Once it was low on cash on a Friday, but otherwise it worked great.
Used my Sparkasse card from Germany at Santander. Everything worked fine-no issues.
Used Multibanco twice-once it asked for conversion, once it didnt-and still got hit with a high fee. Always take a receipt!
ATM was almost out of cash on a Friday. I only got €100-barely enough for the night! Plan ahead.
Multibanco charged me a fee even though I declined conversion. I used my Monzo card-avoid if you can.