I would like to submit a package to CRAN using devtools::release and omit a few files and directories from the submission. When uploading a package to Github, files and directories can be excluded by listing them in .gitignore. What I am looking for is the CRAN counterpart of that. Judging from the explanations on this site, listing files in .Rbuildignore only excludes them from the package bundle, but not from the CRAN submission.
You are still right about .Rbuildignore. If you use devtools::build(), it will only build files not in .Rbuildignore. So that built file is ready to submit to CRAN.
I even think devtools::submit_cran() builds as well, but I'm not sure about that.
After submission, you can check the status of the submission here: https://cran.r-project.org/incoming/. If it's your first submission, the package will be in https://cran.r-project.org/incoming/newbies/.
Better yet, check your submission on this dashboard: https://lockedata.github.io/cransays/articles/dashboard.html.