A lot of talk led to this, Paid features in opensource apps - #91 by Licaon_Kter
Note: Pinboard is a paid subscription service, an account is needed.
in this old app:
PinDroid (Bookmark manager)
Now there is this newer app, but it does not have the Note in description? Is it not a paid subscription service with account now? It does appear to be one on website.
Share to Pinboard (An app with a single purpose: to send URLs to Pinboard without a fuss.)https://f-droid.org/packages/com.bikodbg.sharetopinboard/
Consistency is overrated, but sometimes it should be.