I have setup a PRI to SIP channel before using elastix (now discontinued and bought by 3CX I think).
This needs investigation, but - Over the top of my head, I think you could probably have some kind of a 4G/5G modem hooked on to an SBC (Pi, APU, etc.) and then forwarded to your SIP line which you can pick over IP (Internet), this should work.
One of the child comments mentioned DID (Direct Inward Dialling). I am no expert, but if your Australian provider supports something similar, you will get the number (friend) who is dialling in, instead of your own Australian number dialling in to your receiver phone. This is useful for caller ID, otherwise it's just like a forwarded call.
This needs investigation, but - Over the top of my head, I think you could probably have some kind of a 4G/5G modem hooked on to an SBC (Pi, APU, etc.) and then forwarded to your SIP line which you can pick over IP (Internet), this should work.
One of the child comments mentioned DID (Direct Inward Dialling). I am no expert, but if your Australian provider supports something similar, you will get the number (friend) who is dialling in, instead of your own Australian number dialling in to your receiver phone. This is useful for caller ID, otherwise it's just like a forwarded call.
Hope this helps.