Before commenting at bugzilla, I wanted to check back here since I cannot replicate this problem.
Here is what I can do: I can use my mouse to select Tools>Macros>Record Macro then immediately press, say, ctrl+shift+left arrow. I see the selection highlighting expand to the left. Then I press up arrow and see the highlighting collapse and the cursor frame move up. Then I type 45 enter and 45 is entered. I use my mouse to click on Stop Recording and after giving a macro name, etc., every move is recorded.
I also tried assigning Record Macro and Stop Recording to keystrokes. Everything still works without touching the mouse at all.
Everything seems to be correct and as I would expect.
Version: 220.127.116.11 / LibreOffice Community
Build ID: 499f9727c189e6ef3471021d6132d4c694f357e5
CPU threads: 8; OS: Linux 5.16; UI render: default; VCL: gtk3
Locale: en-US (en_US.UTF-8); UI: en-US
Ubuntu 20.04 LTS with kernel upgrade from 5.13 to 5.16