Hallo!
This site contains TESTED resources to learn Amharic online compiled in 2021
How To Learn Amharic + Best Courses And Books (mezzoguild.com)
General list of resources and manuals, however, the date of publication is unclear. Below I added more resources I have tested myself.
FSI Amharic Basic Course (fsi-language-courses.org) or Live Lingua Project (www.livelingua.com)
FSI Amharic was originally created for US diplomatic staff who took intensive 6 months courses. It is the only specialised and systematic manual to teach Amharic available for free online. For best results it is needed to print bundle of lessons and listen to the audio. Ethusiastic learners have introduced some of the content on Memrise app. You can play on your phone with these excelent exercises that include audio and the Amharic alphabet! Basic Amharic with audio - Memrise
English - Amharic for beginners (50languages.com) + STEPS in 50 languages - App on Google Play
100 comprehensive lessons including audio, the alphabet and exercises on the phone app available for free and developped by Goethe Verlag GmbH. My only complaint is that it has standardised sentences translated for all languages and has no specific explanations of the Amharic grammar. The phone app is a good exercise for language exposure and practice but for a solid understanding and learning you still need a specialised manual or tutor.
Learn Amharic Online – AmharicTeacher.com
Nice resource for very basic vocabulary and the alphabet, with quizzes.
Easy Amharic Lessons For Beginners - Youtube play list