Getting access to dockerized Rstudio server GUI through a VPN

This is still challenging me. I have read: R studio server, can't forward to port 8787 but still do not have a viable solution.

Again, local A -> ssh -> VPN -> B --> docker rocker/tidyverse -p 8787:8787 -it -> C
Want to get browser from A to list to C's port 8787
Port 8787 is ufw allowed on B and nmap shows 8787 active on both B and the docker container.