Self host FreshRSS, use the GReader or Fever API link that’s built into FreshRSS to sync to other apps on your local network. If you want to access the sync remotely, use Tailscale or setup Wireguard. I personally just run Wireguard in OpenWrt
There is no need to expose FreshRSS to the internet
If you want free, I’d recommend Protom Mail.
For paid, I really like Mailbox.org and Posteo. They work with IMAP/POP3, CardDAV, and CalDAV