Is there a way to automatically switch to 4G when 5G outages occur?

[arggg]

I recently took up the Telstra 5G home internet plan ($85 a month). It is much faster than my previous fibre-to-the-curb NBN and I am very happy with the service. However, it does experience outages now and then. I am running an important piece of software that requires that my internet be always on (any downtime costs me money). The NBN smart modem had 4G backup, which was great. 

My question is: How do I set up a 4G backup for when 5G goes down? Is there anything like the 4G mobile dongle for business that works with the 5G home internet modem? 

I can hotspot from my phone, but I need it to work when I am not here/asleep, so this option is not optimal. 

Thanks in advance. 

[Jupiter]

I can't find anything that mentions that the modem will drop back to the 4G network. All the documentation available only mentions the 5G network.

Also, the documentation doesn't mention the ability to use a USB dongle with the modem either. I am fairly confident that the functionality is not available.