I used to have a setup that spanned 5 monitors across three computers (dev laptop with two external monitors, and two all-in-one PCs to test the code). I used a piece of software, can't remember now what it was called, but it linked the three computers together so I could use the same mouse and keyboard across all three. It also allowed you to custom arrange where the monitors were so you didn't have to just have them all lined up perfectly. Here's an earlier version of the setup, before I got the second AiO PC:
At another point I had a home setup using a USB dock and a USB switch to make it so with a button press I could switch my monitors (and most and keyboard and speakers) between my personal desktop and my work laptop.
Edit: I don't know why my keyboard decided I wanted to write "Ayy". I have never typed that in my life. Well, until just now
I want to be able to poke around on the personal while on work conference calls... But would love to have the ability to share mouse and keyboard without using Logitech's native software.
You basically just load software on all wanted systems and tell the software where their screens are and you can seamlessly move your mouse from screen to screen and system to system. You can optionally allow it to keep the clipboards in sync too.
I got in on it like 10 years ago as part of a crowdfunding campaign, but they're still around and look to be relatively reasonably priced.
I do exactly this, and I have for years! It's a work laptop, so I can't install whatever I want. I have a dedicated mouse for the PC and another for the laptop, hdmi switch for a shared monitor, but also a dedicated monitor for both as well. Then a shared keyboard on a 4 port is switch.
You can get a USB hub that can switch between 2 devices, that's what I am running in my current setup. But you have to manually switch between them obviously. Or you can use peripherals that has multiple device support but if you already have a good device then just stick to the hub.