VoLTE is already used in the UK - my iphone 12 uses it if available; if not it just drops to 2G/3G to make the call.
I suspect that, despite what is being said publicly by Jolla on the implementation of VoLTE, they are already planning or working towards implementing VoLTE as soon as they can. It will simply not be credible to sell a phone OS that … ahem … will not be able to make phone calls. Can you imagine the damage it would do to their public reputation (even if their current target market currently does not require VoLTE) if they didn’t? We learnt today in the community meeting that Jolla are only really concentrating on corporate business customers and not consumers. How many new business customers do you think they will get when they try to sell a phone OS that can’t (or soon won’t be able to) make or receive phone calls? No business would take the risk, especially ones where their employees internationally travel. Reviews of the OS would be panned and Jolla’s credibility for selling a modern alternative phone OS would disappear fast. If they are genuinely have no plans for VoLTE then it will either be a sudden coffee selling moment or EOL for sailfish for anything but a hobby OS.