There are a few strategies you can use to extend the life of Access and make the app available outside of a LAN.

Utilizing Remote Desktop of some kind:

One way is to use Remote Desktop services. I often just use a VPN to get into a particular LAN where Microsoft Access is being used and have a system that is already there set up to allow remote access.

There are third party programs that can provide connections like this without using a VPN like Splashtop for example.

The benefit here is that you can continue using the app in the same way you have been, in exactly the same way with no changes to Access at all. You will have to purchase licenses for Remote Desktop Services or the third party software and make sure you have a reliable computer that is left on OR you can always use a virtual machine. You can even use a virtual machine in the cloud via Azure. Again, the main limit here is the cost.

Putting your backend on the public internet

Another way to use Access remotely is to utilize remotely available resources. This again would mean something like Azure SQL Server, or some web server with MySQL exposed or some similar database server (SQL Server comes to mind as well).

This also could require new licenses and you would want to know what you are doing if you are allowing public networks to connect to the database server.

You would want to make sure you were encrypting your connections and data, and know how to set up and use authentication securely.

In this case, when you are using servers publicly available on the internet, data latency issues become very important. Negligible / trivial operations on a LAN become problematic when communicating with a server much farther away. Latency issues means that it might take 10-20 ms to connect to your server on a LAN while it might take 400 ms when communicating with a server hundreds of miles away. If the application crawls to a halt, you’ll need to start looking at optimizing your connections and transferring more data per transaction with the server.