Prior to my first trip (2016), I got an online tutor to try and pound the basics into my head. I have always tried to be able to say something in the native language and have a smattering of Spanish and French.
I must say Portuguese is not necessary as most people you will meet speak English. BUT, if you want to interact with some people (i.e. the policeman, the butcher, the fishmonger, or the owner of a tiny restaurant), some Portuguese will go a long way. Your efforts, no matter how tortured, will bring a smile to their faces.
BTW, don't try to get by with Spanish. That is considered insulting.
You are correct that Duolingo only has Brazilian Portuguese and the differences (although subtle) make it a waste of time.
I tried Memrise last time, but now have enrolled with "Practice Portuguese" and it seems to be better. It is costing me about $16/month and I will work it (hopefully) daily until my trip in June.
I would, if I were you, check out the site and see if it is for you.
Regards,
Dennis