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For DTube, after I post to DTube I usually just go to the Steemit Article version of the DTube post then copy the hypertext that comes up when you click edit, then use it to post my DTube video to WhaleShares, and thus I've posted my DTube video to both Steemit and WhaleShares.

I've been behind in editing videos lately, the other day I decided to post one of my old cat videos from a few years ago to DTube, this is what the WhaleShares version looks like.
https://whaleshares.io/cat/@joey-fancy/tucker-cat-hugs-humans-01
Just like in the Steemit article it creates a link to the DTube video with the thumbnail. (And the link I included to YouTube also shows up as an embedded video just like on Steemit)

There is also a cross posting tool https://masdacs.io/ that allows to the creation of an article can can be instantly posted to both Steemit and WhaleShares, but lately I've been finding it hasn't been working as well with WhaleShares, but it used to work fine for both.

The cross posting tool also allows for posting to Golos and Medium, but I'm not familiar with either of those, however I've been meaning to look into them.