RSelenium RemoteDriver not connecting to port 4445L

Question

I have been following the Docker/RSelenium tutorial here: https://docs.ropensci.org/RSelenium/articles/docker.html

I have successfully hosted my own Selenium server:

# sudo docker ps

CONTAINER ID   IMAGE                             COMMAND                  CREATED         STATUS         PORTS                              NAMES
0c673ba37477   selenium/standalone-chrome:88.0   "/opt/bin/entry_poin…"   3 minutes ago   Up 3 minutes   5900/tcp, 0.0.0.0:4445->4444/tcp   zealous_shannon

When I run the following commands, per the tutorial:

library(RSelenium)
remDr <- remoteDriver(port = 4445L)
remDr$open()

I get the following output with no error message:

[1] "Connecting to remote server"
$id
[1] NA

The expected output is:

## [1] "Connecting to remote server"
## $applicationCacheEnabled
## [1] TRUE
## 
## $rotatable
## [1] FALSE
## 
## $handlesAlerts
## [1] TRUE
## 
## $databaseEnabled
## [1] TRUE
## 
## $version
## [1] "45.0.2"
## 
## $platform
## [1] "LINUX"
## 
## $nativeEvents
## [1] FALSE
## 
## $acceptSslCerts
## [1] TRUE
## 
## $webdriver.remote.sessionid
## [1] "644c353a-34b8-4bb4-bcff-746df5a30af8"
## 
## $webStorageEnabled
## [1] TRUE
## 
## $locationContextEnabled
## [1] TRUE
## 
## $browserName
## [1] "firefox"
## 
## $takesScreenshot
## [1] TRUE
## 
## $javascriptEnabled
## [1] TRUE
## 
## $cssSelectorsEnabled
## [1] TRUE
## 
## $id
## [1] "644c353a-34b8-4bb4-bcff-746df5a30af8"

This prevents me from proceeding with the tutorial. Any idea why my connection via the RemoteDriver is not working properly?