Given that even a corp Mac can now (policy permitting) allow a personal AppleID along with the corporate login, it's easy enough to do the same with just native OS controls even with 2 logins. Something magical about opening an iPad next to a MacBook and pushing the cursor across ... or, alternatively, wirelessly (or USB-C) making the iPad an extended screen.
But Synergy remains great.
If free is your bag instead of supporting the nominal cost:
That "for free" link isn't accurate at all, it claims you have to compile Deskflow yourself, but on Deskflow's Github they offer binary releases.
I don't remember why Barrier was forked from Deskflow, but I've been using Barrier for many many years now. Now that I think of it, I do notice bugs, that maybe I should try out a new version to see if there are life improvements. E.g. with keyboard layouts, even when both systems are running Windows, the target system can be confused what character it should be outputing; and I need to hit "reload" to reconnect after returning one or both systems from standby, sometimes clipboard sharing also breaks.
The keyboard layout issue sounds nastier than the reconnect bug to me. Input forwarding gets surprisingly weird once keycodes, layouts, modifiers and the target OS's interpretation all get involved
Deskflow is just the open source version of Synergy (sans branding) released by Symless.
The weird layout bugs are because of the way it all works behind the scenes. Non-control characters are sent as characters (not key codes) over the wire and then mapped back to local key codes on the receiving side.
As a paid Synergy user, there are tradeoffs (as you probably know). I'm willing to accept these for a side-by-side Mac workflow (or Mac + something else), where each host has a dedicated display.
For a workflow where you are also display switching (kvm etc), Synergy doesn't work well. You can technically use it when hosts are coming on/off display, but it's not designed for it. If you use a kvm-like workflow and have a Magic Touchpad, there's no easy solution without re-pairing, and I hope OPs tool works for this.
Something like Synergy with an HDMI Matrix to allow the number of screens allocated to different computers to be changeable could be pretty interesting.
Years ago I used Synergy and derivatives, but at least back then wireless (as is often needed with at least one machine being a laptop without an ethernet connection or dock) performance was always disappointing, I think due to how it makes round trips through your network instead of using an ad-hoc P2P wifi connection like how Continuity built into macOS does.
Love Deskflow. It has bugs with high-DPI displays on Windows. If the server is a Mac, you may need to launch it with an environment variable DESKFLOW_MOUSE_ADJUSTMENT based on the scale factor of the client.
High-DPI bugs are some of my least favorite software bugs because people usually don't seem to care about them!! but they are so incredibly annoying and infuriating.
https://symless.com/synergy/features
Given that even a corp Mac can now (policy permitting) allow a personal AppleID along with the corporate login, it's easy enough to do the same with just native OS controls even with 2 logins. Something magical about opening an iPad next to a MacBook and pushing the cursor across ... or, alternatively, wirelessly (or USB-C) making the iPad an extended screen.
But Synergy remains great.
If free is your bag instead of supporting the nominal cost:
https://github.com/deskflow/deskflow
They explain this here:
https://symless.com/synergy/blog/how-to-use-synergy-for-free