Hi Brian,
while moving over to Dockerized Versions of ]project-open[ I "stumbled" (after hours of looking) at an unoconv image which runs nicely in it's own container.
https://github.com/alphakevin/unoconv-server
Testing it with curl provided the results I wanted without running so far into the problem of multiple parallel conversions (especially as I might spawn multiple containers in case that is needed).
Still need to change our code though to us ns_http or chilkat (https://www.example-code.com/tcl/http_multipart_form_data.asp) with the container.