I ran a Spelljammer session with new players at my LGS on Saturday, and it featured a ship to ship battle (for reference, check out D&D Beyond
Spelljammer Academy which AFAIK is free, though you may have had to "claim" it, whatever that means.)
At any rate, there were several things that I had trouble with.
1) Siege weapons. Can you really just (as my players wanted to do), fire a Mangonel at the other ship's Captain? The rules say "targets" and don't specify anything about how that's done. I assume that the Captain can hide below decks, but that doesn't seem very captain-like.
2) The other thing they wanted to do is "target the enemies' weapons" (very Star-Trek-y). Unfortunately, the battle would have raged for several rounds before it would be possible to disable the enemies weapons. HP are designed such that a creature or object is "fine" (fully operational) unless it's at ZERO HP, and then it's destroyed. I made up a "damaged" condition, just so they felt like they were doing
something.
3) OTOH, it seemed like it would be possible to fire a Mangonel at the other ship's Mangonel CREW. (See #1 above). At which point, unless they have a backup guy to join the 5-person crew, the Mangonel would then only get to fire every-other round (or so, as it took 5 actions to fire, which could be 5
people using one action each, or one person using 5, or any combo thereof).
I have more to say, but my wife is calling me for dinner. Please comment on that (if you have any understanding of it). I welcome tips on ways you've made it work, if you've run any 5e Vehicle battles at all (I assume that the Decent into Avernus "Road Warrior" cars work similarly. And I know that ships in Saltmarsh do.) Any experiences to share?