Dongle for x4000b bluetooth mouse

I think this mouse is Bluetooth 5.1, not sure. Will a 4.0 or 5.0 dongle also work?

It should as Bluetooth is backwards compatible. But like WiFi, issues can arise. Like signal degradation, and chipset compatibility. I say chipset compatibility because I've had routers and client devices refuse to work together well at all and I'm assuming it was the chipsets in both the router and client device. So having said that, I have reason to believe the same may be true for Bluetooth.

This hypotheses can probably be true if for example you ran a router with the same chipset functionality as the client's chipset. Or the same Bluetooth chipset for both devices. Both devices will play along well with each other with no issues once so ever.

=off topic=

Your avatar looks awfully familiar. I'm thinking from TechIMO?

I'd go IOGear and not such an off beat generic chipset. Especially since I just got done talking about chipset issues with wireless devices. The ethical hacker community knows all about chipsets and their importance... IOGEAR :: Networking Solutions

This might be Broadcom. USB-BT500｜｜ASUS USA Seems to have issues in Linux.

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I utterly hate BS tech specs. It's a massive waste of time. FHSS? (Frequency Hopping Spread Spectrum) Really?! No shit! What about the most important? The chipset?

The frequency band isn't 10GHz? Only 2.4GHz? Ah, shocks. *kicks small rock*

Lowest OS support is 8.1. That's absolute nonsense and code laziness. Well, IMO anyway.