Issues with bluetooth

I find the bluetooth connectivity to be erratic. The device connects and then suddenly disconnects repeatedly with a message that no bluetooth hardware was found in the laptop. I have no such problems with Linux Mint 20.3, which I use on this same laptop in dual boot configuration. Also I find that after configuring power settings to shutdown when I press the power button, there is no response when I press it. Shall appreciate if something could be done.
My laptop is a 6 year old Dell Inspiron 3537 with Core i3 and 8 GB RAM with Realtek audio.

What version of UB are you using? 20.04.3 or 21.10

If 20.04.3 you can move from the HWE kernel back to the 20.04 kernel (v5.4) which is the same as Linux Mint.

When bluetooth disconnects this smacks of power-management issues - you can also turn off auto-power management for bluetooth as well.

There are various bluetooth threads here on discourse - but I would also suggest looking at posting of the official flavour support sites and where the wider audience can also help since bluetooth issues will be across official flavours.