I’m obviously biased as I’m a Jolla employee. But I am using Xperia 10 III as a daily driver. It’s possible to use all three cameras; there’s a patch which allows you to choose between the three cameras and the selfie camera. You don’t have to use the loudspeaker; the echo issue happens very rarely - the last time it happened to me was in June 2022, i.e. over a year ago.
If you already have the device, why don’t you try it out yourself?