Decky Plugin "DeckyParty" may be the easiest way yet to transfer files between your Deck and other devices

The plugin brings the excellent CopyParty, which is a file server program. After toggling it on from the Decky plugin, you can go to the provided IP address on any of your devices, enter the password, and access the Deck's files. You can manage files, upload or download files, and more. File transfer speeds are fast and resumable.

Here's the GitHub for the plugin, although for right now it's pretty bare on a description. For details one what all it can do, I'd recommend checking out the CopyParty link up above.