This (longer set of instructions for ex: https://code.visualstudio.com/docs/setup/linux) shows how to get the repo installed and then goes on to dnf.
This direct .rpm (https://code.visualstudio.com/download) info page doesn't say whether dnf will report updates or whether finding out about avail update notifications is a manual process or whether "I'm on my own" update-wise.
I haven't been able to find any clue or doc that says how dnf check-update handling might differ when the install is done, not via dnf -install, but with rpm -i.
I'm confused about, 'cuz I haven't understood enough or read enough, whether dnf check-update will inform me that packages installed with rpm -i are due for update.
The 1st version mentioned sets up the key and the repo. The 2nd is just an .rpm. I have no idea whether the .rpm alone will get me dnf check-update results. It doesn't say, and vscode updates frequently.