I am looking into options to use outside of the messaging app that is built into my phone. I have heard of security issues and privacy issues being tied to it so I wan't to move away from using it for text messaging. What is considered the most private and secure messaging service or app that I can use on my phone?
If you compare them, overall it would be Signal. The only better option would be to host your own messaging system through Nextcloud. Signal was also just recently banned in China for not wanting to comply with their spying allowances. Signal takes privacy very seriously.
It is fairly straight forward assuming you understand the basics of setting up the network. TechHut has a good one that walks you through the process. You could honestly just read a simple guide and likely get it going yourself. Shouldn't take you more than an hour.