When embedding an H5P outside of h5pactivity, we display a "placeholder" with a play button and a download button. In the forum, some users asked to auto play these packages:

https://moodle.org/mod/forum/discuss.php?d=450214

IIRC, the main reasons to not auto play were:

1. Data usage, the app automatically tries to download H5P packages when they are played unless they're bigger than a certain size (2MB for cell connection, 20MB for WiFi).
2. In the "pre-play" placeholder, we display the download button at the top right and this button disappears when the package is played. If we auto-play all packages, the big packages (not downloaded in the previous point) would never be downloaded, the only way to download them would be to download the whole section/course.
3. Performance. If a teacher adds several H5P packages in the same page, auto-playing them all means rendering many more elements and JS code, and this can impact old devices.

We should evaluate if we want to change or improve this, e.g. we could auto play packages that are downloaded.