I was a long time Roku user and was also frustrated that there wasn’t a Channels client. I ended up buying a couple TiVo Stream 4K‘s since they’re very reasonably priced and started using Channels with those. They were OK but got …frustrating for a variety of reasons though Channels itself ran fine. I ended up going all AppleTV haven’t looked back. Not sure if the Stream 4K’s are any better now. I keep mine around to tinker with but haven’t used them much lately.
I don’t have as much recent experience with the FireTV’s but my advice is to go wired Ethernet over wireless if at all possible.
Apple is polarizing for some people for whatever reason and yes even with the lowered pricing they are expensive but in my experience ATV’s are worth the price not just for the improved Channels experience; most everything runs better (for me anyhow).
And you can pick a refurbished ATV 4K 2nd gen for ~$100.