i am using Ubuntu Budgie 20.10 and having problem to connect Bluetooth earphone(oneplus wireless bullets z)
Yep. https://forums.oneplus.com/threads/one-plus-bullet-wireless-z-earphone.1230302/
I can only assume oneplus have not submitted compatibility with their hardware with the linux kernel.
It says “Plug in a dongle to use bluetooth” … so have you done this?
Sounds like you need to add a USB bluetooth device first assuming that your desktop/laptop doesnt have a compatible bluetooth device itself.
before ubuntu budgie i used Windows it works fine on that (Laptop: Hp pavilion 15 n004tx)
From a quick google search it appears that this is probably a realtek bluetooth device.
Realtek (the company) linux compatibility is pretty poor - not sure why they don’t maintain their stuff in the linux kernel…
That link may give you some pointers how to diagnose what specific device you are using.
Best ask on the regular ubuntu forums since this isn’t Budgie specific - askubuntu.com and ubuntuforums.org