hello,
I am new to nextcloud and linux world.
I have installed nextcloud ( not the AIO) on Linux mint 21.2 cinnamon.
I have a Fios internet to my own router A and from that router I have setup a mesh network using m9deco. router A ips are like redacted and the mesh network assigned IPs like redacted. My linux machine is wired to mesh with ip redacted
With this setup, how do I configure netxcloud so that I can access within homenetwok as well as remotely outside my home network
Welcome to the forum. Please do not do post your public ip. You are asking for trouble.
Your easiest bet would be to use duckdns.org or a similar dyndns provider to have a trusted domain. You’ll need to read the documentation on how to port forward your router and add a trusted domain to Nextcloud.
Other option is to setup https://tailscale.com/ or a similar VPN and add as a trusted domain to your server.
This sounds like a terrible idea in combining a desktop machine as a server, but it is just for playing around that is fine. Did it myself back in the day. 
All the answers you seek can be found by searching the forum or reading the documentation. Good luck!
Really not a good idea for a Nextcloud server. Use e.g. Ubuntu 22.04 LTS or Debian Bookworm.
Here are installation guide. You can customize the one for Ubuntu for your Linux Mint. You use the part of Let’s Encrypt SSL. Also you need DynDNS and port forwarding on your router.
Nextcloud on Ubuntu 22.04 LTS
Nextcloud on Debian 12 Bookworm