How do I convince smartmontools that my SSD is not a hard drive?

When you run update-smart-drivedb it downloads the most recent database from the source site for smartmontools, in theory more recent than any backport.

You should get a reasonable turn around time if you contact them directly ..

From https://www.smartmontools.org/wiki ...

Device Information

If your drive is not in the ​current version of smartmontools drive database you can help to improve smartmontools information by sending a report about your drive to our mailinglist ​smartmontools-database.

We collect info about USB devices that have been successfully or unsuccessfully tested with smartmontools. If you have a device not listed there, please tell us the test result, by editing the wiki page, and/or by sending an email to the ​smartmontools-database mailinglist.