Strange keyboard behaviour with 6.2 and 6.4

[stevef]

I can reproduce what I think you are seeing with the keyboard setting symptoms.

Under the following conditions

Control Panel->Keyboard->Layout tab - set to match my hardware
specifically
Keyboard model  = "Generic 105-key PC"
Change layout option = "-"
Compose key = "-"
Keyboard layout = "English (UK)"
Any other layouts deleted

Switch the 'Use system defaults' between left and right, logging out back in if required.
Checking function in Linux Lite Terminal

switch to the left  - shift 3 = '£'
switch to the right - shift 3 = '#'

How is your switch set ?

Following your suggestion, I can't reproduce the spurious Menu pop up.
I've read about touchpads doing odd things - does your system have one ?

As you suspect software, have you tried Linux Lite 5.x ?