I’ve been using Pinchflat for a while and so far it’s been great for me. It can automatically rescan the channel or playlist on a defined time (like every day or every week), and download new videos. It uses yt-dlp so you can configure all the parameters you want it to use for the download
Self hosting doesn’t mean you should host everything yourself at home, using a VPS you manage (so the data inside it is still yours) is also a viable option for selfhosting. I myself host some services at home and a few others in a VPS.
As for Dyndns, I’ve used a few providers over the years. DuckDNS is the one I’ve been using for 5 years or so and it’s not failed me once. Pretty happy with it.
Maybe you could have a duckdns pointing to your dynamic IP and your domains / subdomains with a CNAME pointing to the dyndns address?