Hello Paul,
I had the same problem on Windows for 2 reasons:
1) OS-level key combinations take precedence over all softwares
2) Depending on the language of the keyboard (here FR with the accents, etc ...), the keys are not in the same place from Davinci Resolve Keyboard
What you can try:
a) you open the Keyboard customization panel
b) [1] on the top right you have 3 small dots: you click and you make "Save as new preset" and you give a name
c) You go in Workspace => Switch to Page and page by page you redefine a new keystroke:
You click at the place of the command, you click on the small cross to delete the command and when the place is empty: you enter the new combination of key (if a combination is already used, you will receive an alert. case, it will be necessary to find a new free combination)
d) you save
e) [2] then you click on the Shift key
(if you used the same keys as me)
f) Then one by one you click on F1, F2, F3, F4, F5, F6 and F7
For each press F, Davinci Resolve displays the (new) command (here Shift F2 see [3] and it is CUT)
If everything is OK. You close and it must work, even if you are in the Media page.
Customization Keyboard.jpg