I do not know either if the “Open Home Foundation” have registered “Home Assistant” as a trademark and if so then in which countries. There is no mentioning of registered trademarks on Home Asssiant’s Terms of Service webpage, however it does mention “other trademarks”, but it does state that the ome Assistant logo and graphics are intellectual property and thus protected by copyright laws, see → Terms of Service - Home Assistant
So I believe that at least their logos/logotypes should be protected by copyright even if it they are registered trademarks and that that by itself gives the legal owner exclusive legal right to copy, distribute, adapt, and display it, and no one else can legally do so without the consent of the legal owners (that can be either the oritinal creator/artist or the person/entity that paid for the logos to be created) as it classified as artwork that is a type of intellectual property protected by copyright laws in most counties.
@GuySie @balloob suggest that you regardless check out and take inspiration from trademark policy and trademarks that the XBMC Foundation has for Kodi and related, they have most posted in their wiki here:
Also try to register “Home Assistant” with at least USPTO (United States of America and BOIP (Benelux).
By the way, I believe it can be harder to get registered trademarks for common words and word combinations, and impossible if they are a single common word (which is why Microsoft can not register “Windows” alone).
Again I do not think that ITead’s use of the Home Assistant badges and logo in their advertising of their Sonoff branded products is malicious or done in bad faith. I assume that instead their product managers and web designers/admins just copied those without considering that it might be copyright infringement and that consent must first be given to use others logos in the promotion of their products, in this case by joining the "Works with Home Assistant "partner program → https://partner.home-assistant.io