Transfer files directly from phone to watch

My phone has a podcast app which automagically downloads files every night.

I don't take my phone with me when I go for a run, so would like to copy these podcast files to my watch.

Ideally, there would be a way to do this using Bluetooth - but I suspect there is not.

I have tried plugging my watch directly into my Android phone, with and without an OTG adapter and with the watch set to MTP and Garmin USB protocols. I have not been able to get my phone to see my watch ana allow me to navigate the file system and copy files.

I don't want to have to rely on having a computer on me to act as an intermediary. Has anybody managed to get this to work?

I am using an Android phone (Oneplus 6T), with Android 9 (OxygenOS).