Different solution to the problem:
I made an association with Konqueror to text/html, moved it to the top of the list (and it didn't work, as described by J-LA.)
Then (after trying several other things, including show in embedded viewer
, and reading this thread,) I clicked 'Edit', and on the 'Application' tab of the dialog I changed the value of the 'Command' field from
kfmclient openProfile webbrowsing openUrl %u
to the more straight-forward
Then I could remove the show in embedded viewer
thing, and the file browser works as I want it to.