That’s kind of what I’m running into as well. I’m considering the Kidde Smoke and Carbon Monoxide Detector (30CUAR-W), which is less expensive than SC5 (by quite a bit actually), and it appears that there is active integration development through HACS. I need to replace 8 Nest Protect units in my home so $70 a piece (or less in multipacks) vs $130 each is quite a big difference in cost. If the SC5 had the same level of features as the Nest, then I wouldn’t question it, but for the same price as the Nest was and not the same level of features, and lack of HAAS integration, I’m not sure I can justify the additional cost.
I’ve looked at a few others (Place), but I’ve read mixed reviews (same sort of mixed reviews for both SC5 and the Kidde), and currently no smart home integration, so this is a tough decision. I’ve seen that Place may be working on Matter integration, but nothing yet.