Try this in terminal:
To UN-enroll from public beta program:
sudo defaults delete /Library/Preferences/com.apple.SoftwareUpdate CatalogURL
It seams i am not enrolled on any program
Could you post the contents of yours
com.apple.SoftwareUpdate.plist
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "
http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>AutomaticCheckEnabled</key>
<true/>
<key>AutomaticDownload</key>
<false/>
<key>AutomaticallyInstallMacOSUpdates</key>
<false/>
<key>ConfigDataInstall</key>
<true/>
<key>CriticalUpdateInstall</key>
<true/>
<key>LastAttemptBuildVersion</key>
<string>13.6.4 (22G513)</string>
<key>LastAttemptSystemVersion</key>
<string>13.6.4 (22G513)</string>
<key>LastBackgroundSuccessfulDate</key>
<date>2024-02-20T05:36:17Z</date>
<key>LastFullSuccessfulDate</key>
<date>2024-02-20T08:02:33Z</date>
<key>LastRecommendedMajorOSBundleIdentifier</key>
<string></string>
<key>LastRecommendedUpdatesAvailable</key>
<integer>1</integer>
<key>LastResultCode</key>
<integer>2</integer>
<key>LastSessionSuccessful</key>
<true/>
<key>LastSuccessfulDate</key>
<date>2024-02-20T08:02:38Z</date>
<key>LastUpdatesAvailable</key>
<integer>1</integer>
<key>PrimaryLanguages</key>
<array>
<string>it-IT</string>
<string>it</string>
</array>
<key>RecommendedUpdates</key>
<array>
<dict>
<key>Display Name</key>
<string>macOS Sonoma 14.3.1</string>
<key>Display Version</key>
<string>14.3.1</string>
<key>Identifier</key>
<string>MSU_UPDATE_23D60_patch_14.3.1_major</string>
<key>MobileSoftwareUpdate</key>
<true/>
<key>Product Key</key>
<string>MSU_UPDATE_23D60_patch_14.3.1_major</string>
</dict>
</array>
</dict>
</plist>
and
com.apple.updatesettings.plist
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "
http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>DidFixPublicSharePoints</key>
<true/>
<key>UpdateSettingsRunStamp</key>
<dict>
<key>majorVersion</key>
<integer>13</integer>
<key>minorVersion</key>
<integer>6</integer>
<key>patchVersion</key>
<integer>4</integer>
</dict>
<key>addedRemoteAppleEventsAccess</key>
<true/>
<key>did_disable_ftp</key>
<true/>
<key>systemUpdateDate</key>
<date>2022-10-23T09:15:49Z</date>
</dict>
</plist>