You may want to check out Libreoffice Draw but with that many pages it may choke. You may also want to try out MasterPDF. That one is a paid option but you can try it out for free.

On their GitHub page it has a list mobile / native apps that can access FreshRSS.

I’m using pivpn inside a Debian container in Proxmox instead of using a raspberry pi. You can pick either OpenVPN or WireGuard during install. Mine is running WireGuard with no issues. I feel it’s very easy to use.