That's awesome, but it doesn't seem to work on Graphene OS with ddg browser, it opens amber, I grant permissions, it copies a signature and opens a new and blank browser tab.  

 I've been using it on Graphene OS with Vanadium and it seems to work fine. although I'd imagine other web browsers might give you issues with clipboard permissions 

 On Vanadium I just get a blank white page for nostrudel...  

 But when I allow third party cookies it works fine to load and sign in with amber, great!