Also having this problem. It says my system is outdated, but I'm on Windows 11 24H2, which is the most recent version as far as I'm aware?

i can't update firefox to the new version

You appear to be using a Ubuntu package build of Firefox 93.0. The updates are in the package manager and not provided by Mozilla. If you are not getting anymore Firefox package updates in your updates package manager then your version of Linux distro may be EOL with no more package updates.

You can try and update your Linux distro to a current version. Or you can try to use the Firefox tarball from Mozilla https://www.mozilla.org/firefox/all/desktop-release/

The basics is you extract the tarball then run the firefox script or firefox-bin to start Firefox. You can create desktop or such launcher shortcut to it and there are Firefox icons in the firefox/browser/chrome/icons/default/ folder. The chrome in this case has nothing to do with the Google Chrome browser. Oh and make sure the firefox folder has read/write permissions for the user to get internal Firefox updates from Mozilla otherwise you will have to do so say as root. An popular place is to have firefox folder in /home/~ if you are the only user.

Also this will not just replace any package build of Firefox you have installed (in package manager) on your Linux system as they will be separate.

Also having this problem. It says my system is outdated, but I'm on Windows 11 24H2, which is the most recent version as far as I'm aware?

Your problem is not the same, more so when you are using Windows 11 and the OP is using Linux. Please start a new thread and explain more in detail on what you are seeing so people can better help you. https://support.mozilla.org/en-US/questions/new/firefox/form