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
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.
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.