Hardware to play vinyl through HomePods

Apple does not make any Airplay transmitters to connect to other devices like turntables and send audio to HomePods.

There may be 3rd party alternatives though not sure of that, but none would be made, endorsed or recommended by Apple.

HomePods are not regular bluetooth speakers, and AirPlay compatible devices that could connect to them are to my knowledge limited to Macs, iPods, iPhones, iPads and Apple TVs.

Yeah, other speakers and receivers can work.

The HomePods don't even have wired inputs usb or audio of any kind.

Apple has very specific uses in mind for HomePods, but if you provide feedback they may choose to include a wired input in future versions if enough people suggest it.

click here ➜ Feedback - HomePod - Apple

there are ways, but how well they work I can't say

try reading

Airplay Transmitters? - Apple Community

Amazon.com : airplay adapter

AirPlay transmitters? : r/HomePod

more

Airplay transmitter - Google-

thats what I do with sonos it has an usb-c audio input and with an adaptor and a turntable with an rca to minijack cable to a minijack to usb-c adaptor I can play the audio out of all the configured sonos speakers.

why apple do not make such a device I can't say, one could say the same of dvd and tape decks I suppose

you can suggest it to them using their feedback channels

Product Feedback - Apple