The easiest way to learn piano is to use the Beginners MasterClass method, which has proven extremely effective for our senior citizens piano community, for both absolute beginners and also people with some previous piano experience.
Many of our students in their 70's and 80's can pick out a tune on the piano but don't know what to do with their left hand. With DecPlay you'll learn that the left hand plays more notes, but they are in incredibly simple patterns, so they are quick to learn.
As an example, Betty could pick out a tune quite well but didn't know what to do with her left hand. After joining the course, she was able to play songs like Amazing Grace and Silent Night with both hands within days.
Also Eric joined and although he could read notation, he found it hard adding in his left hand. Here's a video of what they had to say about the Beginners MasterClass https://vimeo.com/492438998
My advice is to use the Beginners MasterClass method that makes adding the left hand easy, without having to read traditional notation.
You can see a taster of the course in the Seniors Workshop video
A summary of the course content is at https://decplay.com/seniors-bundle-details/