Is there a wireless Apple mouse that works on a 2020 27" iMac on Sequoia?

It shouldn't matter whether or not your iMac is an Intel version. The only stipulation, that I'm aware of, is that it must be running macOS Sequoia 15.1 or newer to be fully functional.

As far as Logitech wireless mice, the newer ones can work wirelessly by either Bluetooth, or via the Logitech propriety Logi Bolt wireless receiver. Previously models also work with Bluetooth, but had the Unifying receiver instead. FWIW, I currently have a Logitech MX Master mouse and use the Unifying receiver for connecting to my M2 Pro Mac mini. It also connects perfectly well to either my Intel-based MacBook Pro or my Windows PC tower.

Yes. The current Magic Mouse will work just fine. I have one from my 2017 iMac that works beautifully with my new Mini M4.

05Mark2 wrote:

[...]On another subject, is it safe to assume Apple won't provide OS updates beyond Sequoia for the Intel 27 inch iMacs?

[Re-Titled by Moderator]

We can expect support will be dropped before too long. We'll know more when the next OS is released, likely later this year.