What's the best way to upgrade Bitcoin Core to version 31.0?

I wasn't sure where to grab the official Bitcoin Core download, so I just went with what I found. Right now, I’m on version 30.2.0. I didn't even realize version 31.0 was out until I saw it just now. I want to upgrade, but my blockchain sync is nearly halfway done, and I really don’t wanna lose that progress or have to start the sync all over again. What's the safest way to update without messing up my current sync? Can I just download the new version and install it right over the existing one?

Close Bitcoin Core properly, wait until it's done, then install the new version and just restart it.

You can download and upgrade your client without affecting your sync, your sync will continue from where you stop from your previous sync. When doing installation of new version, make sure you direct your client to your Bitcoin folder where blocks and wallet is saved on your pc just incase you didn't keep it in the default directory.

It's puzzling that you somehow made it in an old release announcement thread which isn't even the currently pinned topic in Bitcoin discussion board. It's even buried down to page 17 of that board. Google search's fault? Yeah, But close any running instance as they said. And it's rare to have incompatibilities but, there's extra note sometimes in the "release notes" directory of the bitcoin repository, so you may check it when upgrading if you have the time. v31.0 release notes: github.com/bitcoin/bitcoin/blob/master/doc/release-notes/release-notes-31.0.md#how-to-upgrade Also, what you've asked is included there.

I usually don't rush to update my Bitcoin Core nodes when a new version has been published, unless the new version fixes some severe vulnerabilities that require swift updating. So, I'm not in a haste to update to Core v31.0, still fine with running Core v30.2. Maybe after 4-8 weeks I consider an update to the newest version most of the times. That's just my routine, YMMV.

On Linux if you unpack the Bitcoin Core archive on top of an existing installation, it's not going to touch your bitcoin.conf. So no need to double check your settings unless something deprecated was removed. Same with Windows when you install a new version of Core. macOS I don't really know, but I imagine it's the same.

i done it with macos. but like core 21 core 23 core 28 core 29. i am on core 29 right now. and when i do it i make sure to move any large amount of btc to my trezor. just like when i upgrade the trezor i move it to my core.

I trust my backups so I don't need to move anything out of a wallet before upgrading. But "large amounts" shouldn't be in a hot wallet anyway. This is the more concerning part of your post: moving coins from a hardware wallet to a hot wallet to upgrade is unnecessary risky. If the upgrade fails, you have your seed phrase to recover your funds.

Same here, I’m still running v29.0 and don’t really see any reason to upgrade. I have a deep rooted paranoia when it comes to anything Bitcoin related. It probably hasn’t been a bad thing over the years.