I had both Xubuntu and Ubuntu 18.04.3 LTS on my ThinkPad T480s and there is a clear difference of the bluetooth performance between both distros. The Xubuntu distro autoconnects and has no problems finding devices, is also faster. Does anybody know why and how I can get the same bluetooth performance / drivers / interface in Ubuntu 18.04.3 LTS as in Xubuntu 18.04.3 LTS?
Here is a video of the behaviour: https://drive.google.com/open?id=1md0_2J5H5dV0w6MdBpUGi9eUyhQMinMr
Chinese proverb: Go the mountain and meet the tiger.
In other words, It is a probably a difficult path to fix it.
Such cases dealing with hardware related issues need specific experience, which only few users may have. So we may not find a direct answer.
Generic path
Look for "debug" & "troubleshooting" instruction
wiki.ubuntu.com - DebuggingBluetooth
May check other distribution with same stack
wiki.archlinux.org - Bluetooth #Troubleshooting
An interesting tool hcidump to get verbose logs, check for use cases here in AU or Unix.SE.
Note: Documentation changes slower than tools themselves, so watch for last update date on web-pages and trust local man-pages.
Most debug instructions at some point, ask to test the edge development code or binary build.
If the Bluetooth device is a USB one (like major laptops), then it is possible to try any testing setup without touching your current production system using VirtualBox with the extension pack.
Ask Ubuntu a question or Submit a Bug Report (Ubuntu/LP or may be Upstream project). This is up to your evaluation where previously collected data are leading to.
There are hundreds of bluetooth posts in Ask Ubuntu but we can narrow it down to your needs:
The 18.04 answer here describes how to make the device auto-connect from the command line and then how to incorporate it into an automated script with no human interaction.
For 16.04 users a similar answer exists:
If you have problems in 18.04 with blueman automatically disconnecting this might be helpful:
