Thank you Eleftherios,
I’ll give the beta program a go on the Nokia to see if that provides a solution.
I believe the Raspberry Pi is a fully supported solution for up to 8 simultaneous calls. Currently I only have one sip trunk and 3 extensions on it. Performance has been very good with this setup. The only exception being the Nokia 8.1 cellphone which seems to be having some network issues. Production deployment for my organization will be on better hardware. I note the Raspberry Pi can also be used as an SBC for up to 20 devices.
What has your experience of 3CX support been like?