What I usually do is package my models into an R package and install that in my container. I then expose it through plumber. If it is too big, I put some code at the beginning of the plumber file to load the models and other related data for a storage bucket using a service account.
If you mean deploying models by uploading them through a plumber API, that could be also be done but you would have to think about the workloads, memory use, etc.. just.
Happy to discuss it further from a devops perspective.