I think a beginner should only start out on acoustic if that player intends to make acoustic bass the focus of their playing in the future. If you plan on playing electric, play electric. It’s what most bass players will be playing like 90% of the time, so developing those techniques early on is obviously in most players’ best interest.
I do think that, once a player is comfortable with electric bass, that player owes it to themselves to give acoustic a try. Not only is it another weapon in your sound and technique arsenal, but it will definitely help with attack consistency and finer points of fingering and such for cleaner playing and good timbre.
A decent acoustic bass is pricy, I say don’t bother with one if you don’t want to spend at least $800-1,000 on one (not terribly beginner friendly, generally speaking), as I’ve never played one that felt or sounded acceptable under that price point. They’re also, by nature, harder to play, being larger, more cumbersome, and requiring higher string action and more consciousness of the placement of one’s plucking hand and fretting fingers to achieve a good tone.
If a player DOES intend to mostly play acoustic, then there’s simply no substitute. Just be aware that (aside from a VERY few exceptions) they aren’t meant to be truly acoustic and the factory electronics almost always sound terrible, so you’ll almost certainly need to upgrade them and learn to play an acoustic instrument amplified (mitigating feedback, keeping weird noises to a minimum, how to set up and EQ an acoustic rig, etc.) if you want to play with others and be heard. Oh, and immediately fling the stock strings into the very nearest appropriate receptacle and replace them with nickel rounds (ideally, in my experience, GHS Pressurewounds, which aren’t quite roundwound and bridge the gap beautifully) or stainless flats for a good clean acoustic bass guitar sound or nylon tapewounds (Rotosound TruBass are the best I’ve heard or felt) for more of a thumpy, upright-esque kinda deal.
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