The AAC codec is a standard codec and is widely used in various audio applications, including Teams recordings.
It is important to note that Teams recordings in Government 365 may have additional security and compliance requirements. These requirements may include the use of specific codecs or encryption methods that are not used in standard Microsoft 365.
You can check the codec of your Teams recording by right-clicking on the recording file and selecting "Properties". On the "Details" tab, you will be able to see the codec information. Also, you can try to open the recording in a media player like VLC, it will show the codec information in the media information section.
It's also worth noting that Microsoft Teams records in MP4 format. These files are created by the Teams application and use the H.264 codec for video and the AAC codec for audio.