Da Nang has been talked up by certain YouTubers since before Covid. And it does have a lot going for it, it's a great place.
BUT - as has already been mentioned here - Vietnam currently doesn't have a retirement visa. There's talk about it now and again, but nothing has materialized - yet?
That pretty much limits the place to retirees who have married a Vietnamese, as they can get a TRC (temporary residence card). And to those who are willing to do visa runs, but eventually they tire of it or Vietnamese immigration denies their next back-to-back tourist visa.