Preparing shiny app for upcoming breaking package version

I should add that unfortunately, using renv and continuing to base the app on the previous package version is not an option for me, because of the Box-based workflow that my organization uses (explained here, but basically Box does not allow syncing of particular files that are included in package libraries). So I'm looking for a solution to this that doesn't involve renv, even though I'm aware that using renv is probably the "correct" answer.