I have a HomePod in my master bathroom. It gets very humid in there during a shower even with the ceiling exhaust fan running and I don’t have any issues with it so far. Not sure how white will do in the long term but all my HomePods are in Space Gray and I don’t see an issue with it discoloring. It all depends on the size of the bathroom and what you need it for. My master bathroom is HomeKit automated just because I’m a geek when it comes to this stuff lol. I have a HomeKit TV in there that I send audio to the HomePod, a towel warmer hooked up to a smart plug, my lights, exhaust fan/ceiling heater are hooked up to lutron switches, Aqara temp/humidity, light Lux, motion sensor controlling automations, etc. In my office (aka master bathroom) the HomePod sees a lot of action lol. Music, taking calls, setting scenes, TV audio... Was thinking to put a Mini in there but not sure it will be enough HomePod. I’m not even exaggerating lol.
malcky77 makes a good point about outlets. Just had my bathroom redone and specifically asked the contractors to add a few in strategic places with GFCI. Generally, that could be an issue.