Hi Ingram,
I am currently playing around with the sample document of my biblatex-archaeology styles, trying to convert into ODT. In the MWE attached after the first call of \footnotemark there are most spaces missing in the entire document ( outfile: https://ingram-braun.net/test/make4ht/footnotetext.odt ). This happens in biblatex' \footcitetext(s), too, then.
I can confirm this issue. TeX4ht seems to ignore spaces before \footnotemark and \footnotetext, but if you don't use \foonotemark, the command that should stop ignoring of the spaces starts their ignoring instead.
Try to put this version of ooffice.4ht to the directory with your TeX file: https://gist.github.com/michal-h21/2b9130b736146db57862ea21f26a628f
It should fix the issue in your MWE. If it works, I will update TeX4ht sources.
Best regards, Michal
