you must mean open hardware and source sim ?
because the sim is a micro computer in itself, with it's own cpu, ram etc.
Also here even if we had an open hardware sync and all source open the issue reside in the network itself, so even there they could track you.
we can only fix this by disabling anything before 5G SA, as the SS7 issue was only fixed on 5G SA, so even 5G NSA is vulnerable as it reuse the 4G config.
NSA for Non Stand Alone