An irregular reminder that calling this place "Mastodon" has a bit similar energy as saying "I just sent you a GMail."
"Fediverse" (or "fedi") is a better term.
Mastodon is just one of many software projects that talk to each other to create this multi-instance social network:
https://axbom.com/fediverse/
(kudos to @axbom for this fantastic infographic!)
There are blogs, Reddit-like communities, video instances and many more, all part of fedi.
@rysiek @axbom This is super exciting! I see I can start a blog with WriteFreely and have it naturally interact with Mastodon, through this fediverse system.
I've been waiting for this kind of thing since forever! We have been stuck with corporate bubbles for so long. And now finally.. what a time to be alive :)
I know approximately nothing about internals of that plugin. From what you're saying ("couldn't generate a valid URL" is very vague and doesn't tell me what context did that happen in) I would wager that there's some confusion around the domain that should be represented by the blog (i.e. the domain in the blog's @something@domain address).