Hey there.
Since a week or so I’m using a Xperia 10 ii as daily driver (with some quirks, but ok). I’m wondering if anyone is using this Phone with 2 sim cards in the slot and at the same time a SD card.
I searched for it but found no satisfying answer. With some older Sony phones this was possible when cutting the second sim card a bit; but newer ones seem to deactivate the SD functionality when a second SIM card is detected.
Any experiences?
I’m surprised they physically fit. It is definitely not meant to work (silly limitation, but none the less).
IIRC my XA2 Plus - Double Sim has an additional slot for an SD card. Haven’t inserted one yet but should definitely work without cutting anything.
The 10 II only has the either/or slot for SIM2 or SD (the modification potential I’m not sure about), unlike some (all?) of the big XA2 variants (like my cranky XA2 Ultra) that have room for all 3 cards at once by design.
I’m a bit irritated at Sony. though, for not figuring a way to remove and replace the SD without taking out the SIM(s) and therefore requiring a device restart. 
Probably it’s a matter of available space. Just my guess.
In the 10 II, that very well could be the problem. But at least in the XA2 Ultra there’s plenty of room. The SIM tray door is more than 2x as wide as the SIM tray, since it also covers the push-in push-out micro SD slot. Divide that into two doors (or whatever, I’m not an industrial designer for good reason) and they’d be home free.
What about eSIM integration and SFOS? I have it on the Cosmo and it works well (at least under Android)
Does any Sony device have eSIM capability? I can’t find any info to suggest that any do. Checking the specs of the Xperia Pro, a $2500 (!!!) device, shows no eSIM support. So any eSIM capable devices would have to be community supported unless there’s some unanounced Sony in the pipeline that would also be released to the "open " program.
Huh, in addition to your Cosmo, the Gemini PDA does. And the AstroSlide (giggle).