This webinar outlines three of the most popular open source Learning Management Systems and identifies features and affordances of each.
Google Classroom (Education and Basic Suite), Canvas Instructure, and Moodle by LearnIT2Teach are covered.
Making the decision of which platform to use means doing some research and finding out which will be the best for you as the instructor (because you'll be the one developing it) and for your Adult Newcomer Language Learners (because they'll be the ones navigating and using it).