Maybe it is time to optimize my home wifi. 
I just wanted to chime in here too: over MTP, I can never get DO to load anything except the top-level folder. i.e. mtp://DeviceName/Internal shared storage shows the list of folders/files, but any folder below that I navigate into just shows as empty.
I never have this issue with File Explorer. In fact, MTP is the only thing I still use File Explorer for.
("No issues with File Explorer" with the caveat that I'm aware that MTP can be finicky, so I intentionally never open more than one MTP window at a time, never try to refresh/cancel once it's started a process, never try to do more than one thing in parallel, etc. Even with those limitations tho, I cannot get DO to work over MTP).
The MTP issues is the key reason why I'm not upgrade 12 to 13 with my money. Android Phone and Nintendo Switch Homebrew must use MTP connect every day, it's a frequently used features