I’m in a similar situation: the SIM slots in my Xperia X stopped working, and I’m considering my next move (while I am getting by with an old LineageOS release on an ancient Wileyfox Swift: I am finding this quite hard work 
). TheXperia 10 III does seem like a nice device.
I am worried by the many reports of problems with SFOS 4.5. If anyone can clarify whether a newly-flashed Xperia 10 III is a good daily driver (as opposed to one that has been updated from 4.4) it would be useful.
I would also be interested in hearing about how well Android support works on this device. (@pa4wdh I hope that this doesn’t look like I am trying to hijack your thread, but it seems best to keep requests for comments in a single thread 
)