@Rabbon Thought it might be helpful to you and others to share this comment from the creator of Downrush (shared on Facebook on 12/30/2020):
(highly recommend joining the FB group if you own a Deluge or have one on order, that’s where most of the community seems to prefer to discourse)
I haven’t been working on Downrush for awhile now. The biggest reason is because I myself have stopped using it.
One big reason for that is that the FlashAir card does not work very well with my MacBook. When the FlashAir is active, my wireless mouse often stops working.
Another reason for losing interest in Downrush has to do with the fact that Toshiba is discontinuing the FlashAir product, which is causing the price of existing cards to go up.
So what to do next?
The best set up for a future Downrush involves exploiting the fact that modern web browsers have decent Midi support. Access to SysEx messages is possible as long as the web site involved uses HTTPS (encryption).
An ideal setup would be for Downrush to be served-up from the web, running in the browser, using SysEx messages to access the file system on the Deluge. No information about the files themselves has to go into the cloud.
The SysEx commands we need are: list directory, upload file, download file, rename file, delete file, & trigger reload. While I would love to see Deluge extended to do much more, like allowing you to change synth settings individually, the file manipulation stuff is all I need.
Using SysEx and USB Midi (assuming you can handle a bitrate way bigger than 30K baud) will make Downrush (and many other 3rd party apps) available for the Deluge without requiring users to buy anything.
I encourage everyone interested in Downrush to clamor for this change incessantly.