Ubuntu – Can not access files in any folder on Samsung Galaxy SII

As mentioned on the Ubuntu for Android page, the product is marketed towards handset manufacturers rather than end users. It is intended to be integrated into the firmware rather than act as an after market addition to existing phones.

None of the phones you've listed include the code in their firmware, and I don't think any have yet been released.

MTP is a long tale of misery on Ubuntu. I can't offer a solution to fix MTP (I've tried many), but I can suggest WiFi Explorer instead. You run the app on the device, then point your browser to the URL the app gives you. It works very well and is 100% reliable, unlike MTP.

Mine also intermittently connects with MTP. There's evidently some sort of handshake with the device when you connect the USB cable that sometimes works and sometimes doesn't. When it does, you get the USB symbol in the notification bar and are able to switch between MTP and Camera mode. It IS sensitive to the cable you use, but this doesn't solve the problem, some cables don't work at all, the white Samsung cable is the same as various other cables I have, sometimes it works sometimes (mostly) it doesn't.