I have two computers running Debian / Stretch, which is the code-name for Debian 9. I name those computers ‘Phosphene’ and ‘Klexel’. Debian 9 has just received a major update, from Debian 9.9 to Debian 9.10. At the same time, this update installed a kernel update on both machines.
As far as I can tell, the upgrade went smoothly on both machines.