How do I do a CLEAN install of Catalina

iMac (Retina 4K, 21.5-inch, 2019)

Catalina 10.15.6

I want to do a clean install of Catalina. I set up my new iMac with Migration Assistant. Seemed to work well, expcept there are several issues with the MacOS I can't resolve. So, as a last resort, I've decided to do a clean install of Catalina.

I've created a bootable USB flash drive - pretty straightforward.

I boot my iMac into Recovery mode from the USB flash drive (startup, option key held down) - no problem.

That's it - stuck because neither of my 2 bluetooth Mice will work. Both work perfectly well normally.

And it's a very long time since I ever owned a wired Mouse.

I notice this is an issue which has been around since at least 2017 :-(

Suggest for a clean install of Catalina which are not going to require a Mouse or how do I get a bluetooth Mouse working in Recovery Mode.

Or do I have to find a USB Mouse to get this to work :-(