nitpick: SS7 is used at the core network between telecom companies. Whatever happens at the RAN/RAT layer (ie. 5G vs 2G) has nothing to do with it.
There's still security gains to be had from using LTE, but if mossad wants to hijack your 2fa codes by using a SS7 exploit, thats not going to protect you.
Well, yes and no to the telco core networks. I’m sure you know but for the record - getting access to the SS7 outside telecom companies is easy and fairly affordable (15-20k€/month). That and voice/sms services (vs. e2e encrypted data over virtual networks) grants access to SS7 exploits one under the threat model discussed earlier would want to protect against.
Lockdown mode also does disable 2G[1], although personally it'd have been great to have a 2G/3G toggle per SIM the way they do the other per SIM options.