VNC access to iMac located on home network from remote location

How do I go about using MacOS's built-in VNC (the "Connect to Server" option, NOT the Screen Sharing.app) to remote access my iMac located at home?

I have no trouble remoting in to my iMac while I'm at home using the "Connect to Server" option, but I want to be able to do it while away from home without having to use a 3rd party app like Teamviewer.

The ScreenSharing.app is great for connecting to friends or family members' computers to help them with trouble-shooting minor issues, except it requires that the user on the other end authorize each session. Since I'm trying to access my own computer (while I'm not physically present obviously), I can't use the ScreenSharing.app to accomplish what I want because there's nobody there to manually accept the incoming connection.

I've already enabled the Remote Management service on my iMac, and also forwarded port 5900 on my home router, but typing vnc://xxx.xxx.xxx.xxx:5900 (where xxx.xxx.xxx.xxx is my external IP address) into the "Connect to server" window accomplishes nothing (

I don't have a static IP address or FQDN, so I'm also guessing I would have to take note of my external IP address and lease expiration time before I leave the house so that I know what address to type in while I'm away. If someone can point me to a solution for that issue as well, I'd be eager to learn.

I found a source that suggested setting up a Dynamic DNS client through a 3rd party and provided a list of recommendations, but I'm trying to avoid anything 3rd party.

I'm just now getting into networking and I feel like this is probably a simple thing to set up when you already know the ins and outs, but obviously I'm missing something.

Devices:

2015 iMac 27" Retina (home computer/host)

2022 MacBook Pro (remote computer/client)

router: Asus AX3000

Everything is running the most current OS/updates