Deconstructing legendary gear and weapons should yield a random roll of umbral shards.
Legendary drops are already rare and being able to recycle some value off that luck would be another way for players to achieve progression even if the stats/perks on dropped or crafted legendary gear is not ideal.
I will leave it up to you all to figure out a fair amount of umbral shards per legendary piece.
(This brilliant idea was brought up in @BDLG’s Twitch stream)
Thank you for your time everyone!