IMO, it would be a mistake to buy an AppleTV HD today however, it's surely approaching the end of support. It may continue working, but app developers will stop supporting it. It would make more sense to save your money and apply it to one of the newer 4k models, the road ahead for the Apple TV HD looks pretty rough to me.
Just discovered few details.
HD was sold until last year. This is unexpected as the last delivered HD is then newer than the last 4K 1st gen. By almost a year.
Second HD is in the vintage list of products. Unexpected because by Apple own words “vintage when Apple stopped distributing them for sale more than 5 and less than 7 years ago.”. Clearly not a general rule.
Edit: vintage product description reads “(Early 2016, sold with Siri Remote (1st generation) without white ring on Menu button)”. This is a bit cryptic: HD was released in late 2015 and, as far as I know, only one version of Remote 1st gen exists. So either vintage references HD sold between 2015 and 2021. Since by then was bundled with Remote 2nd gen until last year’s end of sales. Or references an obscure early 2016 release.
Edit2: Just discovered a 2nd SKU of Siri Remote 1st gen was indeed released alongside 4K 1st gen.
As described by this very publication. And bundled with HD. So HD should be vintage for units sold in the period late 2015-2017. And not late 2017 to now. Interesting.
Finally Netflix doesn’t allow AirPlay anymore.
So ATV, or at least Netflix app, functionality better be long lasting.