Sparrowhawk wrote:It's a pity but Daniele's own Mac is not supported by the new OS and so he cannot build a compatible 64 bit executable

But Xcode has been able to build 64 bit executables for many years. I seem to remember that the 64 bit macOS kernel arrived with Snow Leopard, 10 years ago, and 64 bit only (with 32 bit application compatibility libraries) since Mountain Lion in 2012. The hardware has been 64 bit capable since the Core 2 Duo Macs arrived in 2006/7.
The 64 bit only move was flagged a couple of years ago but has been on the cards for far longer.
Of course, it's not only the small operations who have been caught with their pants down on this, there are many large companies who have left it beyond the last minute to transition, as we are finding at work.