Thanks for reaching out about this and welcome to the Community.
Currently, it's not possible to shuffle all the songs from an artist.
You can also consider adding your +VOTE to this idea, if this is something you'd like to see implemented in the future. Despite its current status, you can still add your vote to it and if anything changes in the future, we'll make sure to keep everyone updated over there.
The Idea Exchange is a great way for us to see what our users are interested in and how many people like a certain idea.
Check out this Spotify Answer to learn more about it.
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“Music acts like a magic key, to which the most tightly closed heart opens.”– Maria von Trapp