To share your content inclusively on Mastodon, ad a description to every video or picture/graphic you post. A good description is short but includes all necessary information, so someone unable to see does not miss out on what it is you want to share through your video or picture.
The fediverse service Glitch-Soc has a feature where you can see red boarders around pictures or videos without alt text.
There is also a bot @PleaseCaption@botsin.space that reminds you privately, if you the media in your posts lack a description.