NosyCrow are one of the publishers who have free material available on their website, including a weekly audiobook in instalments, daily picture books on YouTube, craft ideas and activity sheets, daily poems on Instagram and Twitter.
They also have lots of videos on YouTube, including author readings, character illustrations, Q&As, nursery rhymes and origami guides.
See their website for further details
https://nosycrow.com/blog/free-books-activities-and-resources-from-nosy-crow/