How to Abort Installing a Kernel Extension in macOS Sonoma

<Try a Safeboot an see if it clears your warning:  Use safe mode on your Mac - Apple Support 

Login and test. Reboot  as normal and test.>

Update: I ran a reinstallation of macOS while I was at church this evening. When I returned and entered my password, the warning was gone. Everything appears to be working as normal before I even installed XQuartZ. Thanks for that link with detailed instructions! It helped!

The app was XQuartZ. Some app I was trying to install was asking me to install that as well. I was a bit suspicious about it because I thought it would brick my system, and I was right when I found out that the KEXT file was an outdated Apple kernel extension for an outdated X11 environment not compatible with Apple Silicon. Once I found that out, I immediately aborted the installation of the kernel extension, restored the security policy, and removed XQuartZ. (And yes, I did run the official terminal commands for uninstallation, and used CleanMyMac X to clear the leftovers.) However, the warning that it's trying to install system extensions is still there, and I'm trying to clear it. Do you know of a way to do that?

<Try a Safeboot and see if it clears your warning:  Use safe mode on your Mac - Apple Support 

Login and test. Reboot as normal and test.>

Didn't work, so I'm reinstalling macOS.

<What app???>

It was htop, as I wanted a simpler way to adjust the priority of certain apps rather than having to use Terminal. I thought it would be useful, but when I found out the said UNIX app would jailbreak or even brick my system, I aborted using it altogether.

<CleanMyMac X is one of the worst. Installing it is not advised, since it's considered a garbage app.>

Well, I paid for the license, so it's not worth it to not use it. Seems like a waste of my funds.

<I suggest uninstalling all third-party apps that are Cleaners, Optimizers, Anti-Malware, and/or VPNs. Such things are known to cause issues in macOS.>

I pick these apps carefully. If it's a trusted source that's well-known, I'm OK with using it. But for apps that are known to be heavy consumers and cause excess resource consumption problems (such as web browsers) that drain my battery fast, I use App Tamer to help control those when they are not in the foreground. The only apps I don't control with App Tamer are apps that rely on both performance and efficiency cores, such as Apple apps and system processes, or any app by a third-party that relies on both, such as a video game. Before anything else, I rely on the default settings of App Tamer to avoid any potential issues, and I use a 5-second, 60% CPU threshold (out of 200%) for alerts. Finally, if the app is playing sound or my battery is above 80%, I don't use App Tamer to throttle it, PERIOD!

For Anti-Malware, I use PC Matic, as it's lightweight, and is the only app that uses the whitelist-based "verify now/trust later" method, which helps keep me secure by only running apps from a list of apps that are already known to not be malicious.

As for a VPN, I only where necessary, and I only choose VPNs that (a) allows you to choose the DNS server(s) to connect to, and (b) uses interference-free installation methods rather than create a hard VPN profile that typically interferes with things (such as iCloud Private Relay), meaning they shouldn't conflict with iCloud Private Relay (provided you program everything correctly, in which I did).

All of the apps mentioned above are Universal 2 apps, so Apple can manage the resources they receive.

(P.S. — An Apple Support Advisor helped me with programming the settings of App Tamer, and Bing AI gave me an entire list of apps to never throttle.)