Keeping a fork of a repository up-to-date with upstream changes

Question

I have a repository, which is a fork of a public project. The fork contains several additional commits with custom features - nothing fancy. Recently, I have been wondering what would be the best approach of incorporating upstream changes into the fork. Currently the setup looks like the following:

1. The fork has the master branch with these additional commits and another branch that acts like a staging branch (let's call it staging).
2. Every now and then I check if anything new has been released in the upstream repository.
3. If yes, then I rebase staging first (staging also contains all these additional commits). This results in a GitLab pipeline which builds a Docker image and pushes it to a Docker repo with staging tag. After that, a k8s deployment is restarted and the new changes are available in the staging environment.
4. If everything is fine, I repeat the same process but this time I rebase fork's master against upstream master (sometimes I simply reset --hard master to staging).

I feel like the whole process needs a bit of improvement. I was thinking about using custom tags in my fork, but these would be kind of "lost" with every rebase.