Running C8/2.3.9.174. The release notes for 2.3.9.174 mentioned a new certificate was provided that doesn't expire until 2034. Will that allow my connections to my hub to be secure instead of "Not secure"? I have applied this release and rebooted the hub but no change in the security status.
How are you connecting to the hub? If you are using HTTP (say, to the IP address directly--both are common) and a browser that yells at you for HTTP being "insecure" (some are more aggressive about this than others), this will not change anything there.
What it does change is the expiration date of the built-in, self-signed certificate if you use HTTPS (e.g., also to the IP address). A lot of browsers aren't going to like self-signed certificates, either, but for an IP address, it's all you can do.
If you have some other solution set up, this answer will depend on that setup.
If I try to connect via HTTPS, Chrome gives me the "Your connection is not private" message.
According to your message, this may be "normal".
Yes, this does not change that--pretty much anything is going to complain about a self-signed certificate (which is all you can use for an IP address). It just extends the expiration date, so browsers (or anything else using HTTPS) won't really complain about it (more) like they will if it's expired.
Adding this IP address as an exception your browser or using HTTP instead are two simple ways to eliminate that message if that is your only concern. Using a hostname and a real signed cert, which the hub now provides a way to upload, is the "right" way in some sense to do this but difficult for the average home user.