I run into this A LOT. I'm an A/V tech for conferences, breakout rooms, general sessions, you name it. I'm also a pan-techsual tinkerer and all-around nerd. YOU MUST HAVE AN ACTIVE ADAPTER! That said, if your video chipset generates insufficient power on pin 18 (5vdc), like some MacBooks, you need to get that extra oomph from somewhere. The Cable Matters adapter described above is an excellent choice, as it allows you to boost the power via USB if you need it. "Audio out" is a nice bonus, especially if your PowerPoint contains a video! I can run a lovely signal from anything with a full size HDMI. I can use my phone, too, but that takes another powered adapter just to get to full HDMI.
It seems like an awful lot of fuss, but the first thing an output device looks for is a good signal on the power pin. Also, your active converter chipset may run erratically (if at all) without enough juice.
Sorry to say, but while VGA is technically considered an end-of-life technology, those old VGA projectors are workhorses. The rental houses aren't getting rid of them in any forseeable time. /VGA_rant