Yes, but one only needs to write it once, and then everyone could use it. It could probably even be packaged as an official Debian package.
* https://jdebp.uk/Softwares/nosh/guide/commands/convert-syste...
* https://jdebp.uk/Softwares/nosh/guide/converting-systemd-uni...
* https://jdebp.uk/Softwares/nosh/debian-binary-packages.html
...and then keep up with behavioral changes that the Systemd Project people introduce and load-bearing bugs that services end up relying on for lifecycle management.
OpenRC service files are easy to write, and their schema is far far simpler than that of Unit files. [0] It's really not worth the effort to write and maintain an converter, if for no other reason than you need to understand the semantics of both systems' service files to double-check the results of the converter.