Checked today after the updates to the iOS 18 and MacOS 15 platforms to public betas I am now able to download homepod version 18 build 22j531e on all of my homepod minis. I'm not expecting much in way of improvements or features but here's hoping. all I had to do was opt for dev and public beta updates for every piece of apple hardware I own. no appleseed as far as I know. hope that helps clears things up for folks.

Hello all, with the iOS 18 beta 3 I am now able to get the homepods on beta using the home app on my iPhone 14 pro max, however it is only 17.6 not 18 for the homepods. according to what I've read on reddit you need to be on appleseed program to get the 18 os at this time of writing. Anyways update to iOS 18 beta 3 - that fixed it for me :) Cheers everyone for commenting sorry I never got back to you folks and thanks for the upvotes etc etc. Thanks.