Github: https://github.com/raiseCatError/meowdisplay
EDIT 2: I should've mentioned that MeowDisplay started as a fork of OpenDisplay: https://github.com/peetzweg/opendisplay which provided the foundational screen capture, virtual display, encoding and iPhone/iPad receivers. I've since taken it in a more phone-first direction, with work on the interaction, streaming and security layers. I've credited OpenDisplay and its developer Philip in the README under "Built on OpenDisplay".
MeowDisplay is my take on the control your Mac from your phone scene. Available on iPhones, iPads and Macs, with Android rn in closed testing.
The website has interactive illustrative demos if you'd like to see the app demonstrated.
I think MeowDisplay does a few things differently, some of which I prefer and you might too.
Such as Window view: allowing multiple tabs in split-screen type panes. Traditional Mirror/Extend views exist as alternatives. Floating windows: coming in the 2.1 release.
Touch input approaches: Direct Touch(Classic or Natural), experimental Smart Touch, and Trackpad mode alongside Apple Pencil support. Doesn't sacrifice display space for a trackpad, use all of the phone's screen with your preferred mode.
Stage Peek: shows a scrollable and searchable list of your Mac's windows on your phone along with an app drawer when you hold and pull on the left edge of your screen.
It's free and open source so you can try it and see if it's for you without having to commit to it or anything.
EDIT: I've used MeowDisplay during development whilst I was travelling between cities, left my acbook at home clamshell, powered, external display attached, and used it for small tasks remotely, it was pretty reliable even on a 5G network on a moving bus.
Meow, Jai