How do I remove legacy system extensions?

Any app you've installed that places an extension on the drive would be a candidate. There are far too many such apps for anyone here to be able to list all of them.

It also depends on where this extension is. My older brother has this same issue of a now untouchable extension.

This happens when you've upgraded the OS on an older Mac a number of times. When it was possible for apps to do so, they sometimes placed an extension in the System folder. But as of Catalina, the System folder is locked against everything and anyone but Apple.

The result is, the app that installed the extension can't remove it, and neither can you. It's trapped in the System folder unless you erase the drive and rebuild it from scratch.

Edit: Except your Mac shipped with Big Sur, so it was never possible for any app to put an extension into the System folder.

Instead, look in the root /Library/Extensions folder. There should only be two default extensions there:

HighPointIOP.kext

HighPointRR.kext

Not always well accepted but here goes

Start Over from Scratch

For Apple Silicon computer >> Use Disk Utility to erase a Mac with Apple silicon. which this computer appears to be

Heavy handed - Yes

Effective - Yes

Do understand, this will revert the computer to an " Out of the Box " experience

If going this route - I suggest Not using Startup Assist to migrate everything from a Recent Time Machine back.

Personally, I would follow along closely by what @Kurt Lang 👍 is mentioning and suggesting

Worse case and mean worst case

Let us skip the Q&A session, just download the Application Etrecheck directly from the Developer. 

It’s a diagnostic tool that doesn’t change your computer at all.

It gives you a clear and easy-to-read list of both your hardware and software. 

You can get it for free or pay for extra features.

And don’t worry, the report won’t reveal any personal information. 

Once you’re done, just copy and paste the full report using the Additional Text Icon.

i do not ubderstand all this

Find the uninstaller for the software you installed that installed the legacy system extension. Without knowing what you installed, there is no way we can provide anything but generic guidance.

Too much stuff on here do not want to lose all this on here now mayne run its course then

That's a very dangerous statement. It suggests you don't have a backup of the stuff you don't want to lose.

All drives eventually fail. All of them. If your Mac is the only place you have this important stuff, then losing it isn't a matter of if, but when.

Thank you.

The actual etrecheck report is missing

One needs to download the application first

The run the application which will generate a report

In good faith , I shall include and older Etrecheck report jus so you see what it may look like

Never mind the details just what the application actually does

Is the computer still struggling with Avira Security Software or similar ? 

All I know when turning it on says that do not know which one

Yes, I understand you have no idea what you chose to install. Since you don't know, we don't know, either.

You must use the suggestions on the linked posts to try to identify what it is you installed, then contact the developer for an update or uninstall instructions.

System Information has a list of all Extensions under Software, but there isn't a good way to sort out the non-apple extensions. There is a Legacy Software section. It might be listed there.

DODGE01CHALLENGERSRT01_01 wrote:

To much stuff on here do not want to lose all this on here now mayne run its course then

I hope you are not telling us that you have no backups.

If that is what you are telling us, you need to fix that. There's no point in worrying about a message saying that you have legacy system extensions that { aren't supported on Sequoia | might not be supported on some future version of macOS } if you're running without a backup – a safety net.

The message is just annoying.

Forget about erasing your computer and starting over. If you just keep things as they are, but you don't have a backup, you are just one catastrophe away from losing ALL of your data. It is a good idea to make at least two backups of any data that you care about, and to store at least one of your backups in a place which is different from where you have your computer. Even backup drives can fail or be stolen or corrupted; thus the benefit of having at least two.

Servant of Cats wrote:

Forget about erasing your computer and starting over.

Until we actually see what is installed or not installed on this machine

Neither, starting over or continuing to limp along has any technical value.

Yes, it may not need to start over as it could also need to the wiped and started over - No ?

In either case.

Yes, two or more Backups are allows a good practice as you have made known to OP

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