Clocks are a very touchy issue. If you are not hiding, a good clock is very important for security. Most professional networks have independent clocks. Your best option (if you have a serial port) is to build yourself a GPS clock https://www.lammertbies.nl/comm/info/GPS-time.html for about 30 USD. About a decade ago all GPS devices had this featured enabled (had to enable the clock daemon) but you don’t want idiots beeing to secure.