There is now an even easier way than vacuuming. Instead of pulling the unwanted air and moisture from the lines, you can push it out with another gas, which itself can somehow coexist with the refrigerant. I haven't tried it because I already have the pump and gauges, but if I were installing my first mini split, I'd consider it.

Example: https://www.highseer.com/products/pioneer-kwik-e-vac

It's so ridiculously easy to vacuum and charge a heat pump it's kind of unnecessary.

I think I spent $200 in parts on Amazon and have done 4 heat pumps now. It's a vacuum pump, a scale, and a digital manifold/guage. Punch the numbers for subcool/superheat into a calculator and use the temp probes on the lines where they connect to the condenser and you can even skip the scale.

My only caution is this method does not let you check if the lines are leak tight.