https://docs.gitea.io/en-us/upgrade/ gives blank page…
That’s because that page is place holder page that exists to support the article hierarchy, not server content. Notice that that page is not clickable, nor are nay of the other section headings.
You upgrade gitea by simply replacing your current binary with the newer binary. You will likely want to stop gitea prior to replacing the running binary. Don’t forget to restart it when you are done.
Standard best practices like performing a backup prior are always a good idea. It never hurts to read the release notes for the current release, and if upgrading more than one version, I strongly recommend reading the interim release notes for every version between your current version and the one you are about to install.