OK, last one - If you like documentaries and have Amazon Prime, you can add PBS Documentaries to your Amazon Prime video for only $5 per month. It has all the Ken Burns documentaries and hundreds more.
I don't have Amazon Prime, but my local library carries many PBS documentaries on dvd that are available for free. For those who are near a library it may be less expensive to find them at the library.
Note that's a good deal if you subscribe only to Amazon Prime. If you donate to a PBS station, they will let you sign up for PBS Passport, which is the expanded access video service, for around $60 without needing to be an Amazon Prime member.
Otherwise, the standard PBS streaming app is available for free through most services, but it has a limited offering of programs.
After watching season one of Before We Die on Prime/PBS, I was annoyed to find out that the next season requires membership. No thanks. I pay for too much already.