+1 for Jellyfin and Finamp but check out Audiobookshelf for podcasts and audiobooks. It even has regular checks for podcasts that you can set for rss feeds.

Do you have any suggestions for reputable security related websites?

You can use --accept-dns=false flag for tailscale on your parents pihole. That makes it ignore the tailscale dns settings and move on.

It is step 1 on tailscale pihole guide