Monterey was the "current" version of macOS until 2022. That would be typical of Apple support of macOS/OSX. New versions of macOS for about 7 years from release of the Mac model, plus security patches for another 3 years.
The MBP can be updated to a more recent macOS using software called OCLP (Open-Core Legacy Patcher). This is unsupported by Apple and makes significant changes to the internals of macOS. My recommendation is not to follow that path unless your friend is capable of troubleshooting complex issues and then fixing them.