Canon SELPHY CP910 and CP820
For more than a decade, Canon's SELPHY printers have been largely evolutionary. While their bolt-on features have steadily improved (in-printer touch up, better screens, UIs, etc) the core printer engine itself has remained nearly unchanged from the outset. This is most visible when you consider they've used the same media packs the whole time.
The outlier here was the SELPHY ES series; they used different, all-in-one media packs to improve printer handling, but putting aside the physical differences, under the hood it was the same basic print engine, supporting the same print dimensions. Also unique to the ES series were a few minor variations in the printer spool data format, but with the exception of the CP790, the CP series has remained completely compatible for the entire life of the family.
Until the CP820 and CP910, that is. These two use an entirely new print data format (different headers, and RGB instead of CMY data) and despite using the same CP-series media, also sport a slightly different print engine that runs at a slightly higher resolution than the older models.
Another major change is that the CP820 and CP910 break from tradition and no longer need a special driver/backend to interactively send data over; now the whole thing is just dumped over in one big blob. This was an unexpected (and welcome!) change.
Unfortunately it looks like the printers still need some degree of driver-side color management/mapping; figuring that out is going to be tricky. Still, with luck, these printers will be supported in Gutenprint 5.2.10.