Hi @mathiasx@mastodon.xyz,
I was able to fediverse a #Bookwyrm activity to the #twittoverse like you said you tried here 👇
https://mastodon.xyz/@mathiasx/113402214757493277
I first made sure my Bookwyrm account was federated to my #Sharkey instance.
To do that, I have open my Bookwyrm profil from my Sharkey instance using URL : sharkey.world/@curious@outside.ofa.dog and follow myself.
Only then, I wrote the activity on Bookwyrm and it has automatically fediversed into a note visible on my timeline.
#mastodon URL syntax migh be slightly different. Just check it any remote profil you already follow but fediversation is pretty much the same in every software in the twittoverse, so you should be able to do it as well.