I was trying to create a Smart Collection to search and identify all my photos ithat I have uploaded to Flickr. Flicker photos are identifed as such in the 'History' section in the devlopment mode with the following: Publish - Flickr (16/8/2023 09:26:15). A Smart collection, it seems, is unable to read this identification marker.
I suggest that a future edition of Lightroom could have this feature.
Thanks