If you find your video can't play, or that your video will play but there's no audio, it's almost always because your browser can't play the file's video or audio codec. This is the case with HEVC/H.265 video and AC3 audio, which almost all browsers can't support due to licensing issues. Current state of browser support:
So, if you want animebook to play the most video files, the Marmaduke all-codecs builds of chromium are your best bet, and you can install Yomichan on it (instructions below). Otherwise your best bet is Chrome, and you'll need to avoid using HEVC video or AC3 audio with it. And in my experience, while a lot of anime uses HEVC video, AC3 audio is relatively rare, so I've been able to get by with just using Marmaduke and occasionally having to avoid releases with AC3.
Marmaduke Chromium installation instructions:
Animebook now supports exporting flashcards to Anki with a Chrome extension. It's meant to work in tandem with Yomichan, so if you're interested, you can download it here.
To use the Animebook Chrome extension,