Hi André (and Alicia),
There is also no way to inform the target wiki even if the config could be changed, as it is not a local SQL database (this at least might be expected, as WB.C is
separate from Wikimedia). The areas of Direct Access and Wikidata Bridge are ones where Wikibase still seems relatively closely coupled to a local installation, complicating standalone hosting; perhaps some magic could be done
with foreign data wrappers?
As you say, it'd be good to have interwiki support as well. There are extensions that allow easy editing of the interwiki table, and I think doing so would be sufficient to enable links separately, but they're not currently installed on Wikibase.cloud. To work
around external link icons I enclosed links to other wikis in <div class="plainlinks">. A more general CSS override might also be possible (but not JS, yet, as that is not enabled currently).
There was a detailed discussion of licensing issues on the WBStack/Wikibase.cloud Telegram group on August 18, 2021, if you can access that (if not, poke me at @WikiNorn and I can invite you, though I'm not entirely sure the history will be accessible even
then).
Hopefully WMDE can chime in if they have plans to resolve any of the issues you raised, or conversely if they see some of them as out of scope, at least in the mid-term.
Best regards,
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Wikibase Community User Group / WikiFur.com