R mongolite: correct format for connecting with a Mogodb on a remote server?

Question

I'm writing some R code that queries a MongoDB database, imports records matching the query criteria into R, performs record linkage with another data source, and then pushes the updated records back into MongoDB.

The code needs to work with any instance of the MongoDB database. Some people have it installed as standalone on their own computers, while others have it installed on their organisational servers. Note that these are servers specific to individual organisations and not the public mongo server.

To test my code, I have access to both scenarios - one instance is set up on my own computer, and I have several remote server instances as well.

The MongoDB database has some APIs, but I was struggling with the adapting the APIs to include the correct syntax to form my query, so I thought I would try the mongolite package instead.

I was able to create a successful connection string for the MongoDB instance on my local computer, using my user ID (which I retrieve first with an API and save as the R object myids), password, the localhost and port number as below:

# Load library:
library(mongolite)

# Create connection:
con <- mongolite::mongo(collection = "person", 
                        db = "go-data", 
                        url = paste0("mongodb://localhost:3000", 
                                     myids$userid, 
                                     ":", 
                                     rawToChar(password)))

I understood from reading the mongolite user manual that to create the connection string / URI, you skip the http or https part of the address and preface it with either mongodb:// when the Mongodb database is on a local computer, or mongodb+srv:// when the Mongodb database is on a remote server.

However, when I try just changing the prefix and login details for the remote server version, the connection fails. Say the URL for my remote server is https://mydb-r21.orgname.org/ which opens a web page where you can log in to the Mongodb database and interact with it via a graphical user interface. Just swapping localhost:3000 for the web address mydb-r21.orgname.org/ and supplying the relevant login credentials for that server doesn't work:

# Load library:
library(mongolite)

# Create connection:
con <- mongolite::mongo(collection = "person", 
                        db = "go-data", 
                        url = paste0("mongodb+srv://mydb-r21.orgname.org/", 
                                     myids$userid, 
                                     ":", 
                                     rawToChar(password)))

When I try, this is the error I get:

Warning: [ERROR] Failed to look up SRV record "_mongodb._tcp.mydb-r21.orgname.org": DNS name does not exist.
Error: Invalid uri_string. Try mongodb://localhost

If I try changing to mongodb::// (not localhost because it isn't hosted locally) I get this:

Error: No suitable servers found (`serverSelectionTryOnce` set): [connection timeout calling hello on 'mydb-r21.orgname.org:27017']  

Interestingly, the port that is suffixed in the error message is the correct one that I was expecting, but that still doesn't help me.

The documentation in the mongolite user manual and other places I've found online seem to add some read/write specifications to the connection string, but as I'm not very familiar with how connection strings are constructed, I don't know if these are specific to the databases they are using in their examples. I can't find any clear explanation of what the extra bits that are not part of the URL mean, e.g. as shown in this blog. All the prefixes seem to be a bit different too, so I am not even sure what would be appropriate to try in my case.

Can anyone explain why the connection string works fine with localhost:port number for the local instance, but doesn't work with the URL for the remote server / online instance?

Also what do I need to do to make the URI for the remote server valid?