Update: I redid the steps. Made udev rule with nano and called it "dolphinrule.rules". Placed it in directory for udev rules. Reloaded rules and tried also modprobe -r btusb mentioned in Dolphin passthrough for Linux. None had desired effect as there is no signs of a "bluetooth passthrough" as seen in this video at 1m30s.

*heads to Dolphin forums*

NEW ISSUE:

QuoteForcing a specific adapter

If you need to use a specific adapter, instead of using the first Bluetooth adapter that is found, you can force Dolphin to use it by editing Dolphin's configuration file (Config/Dolphin.ini). In the BluetoothPassthrough section, set "VID" and "PID" to your adapter's vendor ID and product ID. These values should be converted from hex to decimal, for example a VID of "057E" should be inputted as "1406".

I located Dolphin.ini at ~/.config/dolphin-emu/Dolphin.ini. But within it I can not find any PID OR VID variables. I need to do this with a adapter I am going to buy. Dolphin forums have not replied to me after many days so I thought to ask here too.

I ended up testing a Belkin 4.0 mini adapter with Bluetooth passthrough. Dolphin page stated it would work if you "force specific adapter". I managed to connect controller through normal emulation but motion aspect did not function well enough to consider it's use. Trying Mario the gamepad controls (not motion) felt noticeably sluggish. It wasn't terribly bad but I was not pleased with it.
I tried to connect with passthrough and it did not pair. I followed instructions, still didn't work. General passthrough was working as the option was visible and I got no errors.

Really disappointed because I tried so hard to get the best possible adapter and make the controller work well. Price is also of importance. Two of the other dongles that are approved more by Dolphin page is not sold anywhere. I then must purchase outside country or/and from private person. It's not only expensive but may also come with tax and fee when importing.

I'll continue searching.

Last update:
I tried following bluetooth devices,
Hama 49218
Belkin Mini BT 4.0
IOGear GBU521

UBUNTU 16.04
I found that NONE of their motion functionality worked properly.

I tested Bluetooth passthrough (forced)and none of them worked. Even though Dolphin wiki claims they do. I'm very disappointed. If anyone is willing to help me redo tests It would mean so much to me.
I added Udev rules. I tested emulation, passthrough, rebooted, tried different usb ports...

If I followed instructions correctly, which I believe I have, then Dolphin adapter tests results are no longer valid. At least not for Ubuntu.

FINAL UPDATE (ISSUE FIXED!):
You need a sensor bar for the motion relating to HUD. This was not stated to be necessary at Dolphin's wiki page. Got a random sensor bar for Wii and it worked just fine.