So your phone BT pairs to the Lenovo, but not the Entroware? And the Lenovo runs Debian, but the Entroware runs Ubuntu Mate?
Assuming this is correct, it sounds like the problem is either your phone, or the Entro hardware, or Ubuntu Mate software. However, the only way your phone is the problem is if your phone's bluetooth connection won't allow more than 1 connection at a time AND if you're still connected to Lenovo/Debian when trying to connect to Entro/Mate. Can you turn off the Lenovo/Debian bluetooth and see if your phone and Entro/Mate "see" each other. If they don't "see", you've got a problem with the bluetooth stack/settings. Is there a fn key to toggle bluetooth on/off? Or a dongle to pull/insert, to verify bluetooth is broadcasting? This would likely eliminate Entro hardware. If they "see", but don't pair, it's likely an Ubuntu Mate or software setting, IMO.
Personally, I've found bluetooth to be a PITA (and slow) for file management. Are you using bluetooth for a specific reason, or would a wifi connection be acceptable to you? And are you using Android? If both answers are "yes", I'd recommend an Android app called "SSHHelper" and/or "SyncME" that connects to wifi and allows 2-way push/pull. I tend to use SSHHelper for smaller operations, or one-shot data transfers; while I tend to use SyncME for larger and repetitive operations, such as syncing my music directory.
From the phone (using SyncME), you can push/pull folders/files/directories either automatically or manually "as desired", depending on how you set it up, using rsync protocols (you can also "sync" data....mirror at both locations).
From your PC, you can do the same by starting "SSHHelper" and using your file manager to "go to location" of your phone's LAN address. I use PCManFM, so I go to "192.161.1.x:2222/sdcard" and mount my phone, and copy files back and forth.
Much quicker than bluetooth, with a lot less hassle. If you want to explore that, I can help. If you must have bluetooth, I'll be less helpful, but do what I can for ya!
Edited by Hedon James, 20 December 2017 - 03:16 PM.