Some of our colleagues brought up the information, and so did our side. Readers report that the HomePod mini is finally compatible with 18W chargers. The compatibility is effective since Update 14.3 (delivered on December 15th). So far, the HomePod mini could only be operated with chargers with 20 W (or more), which still seemed surprising for a device in this category (no extensive calculations such as on an iPhone). However, we note that the spec sheet of the last HomePod mini marketed is still compatible with 20W chargers and beyond.
With regard to the availability of the connected mini speaker, we still have to take care of it patiently: The delivery times have now been postponed to February. Either the HomePod mini is a success, or inventory really is extremely limited (or both) for two reasons.
The HomePod mini is still available from Fnac at a price of 99 euros and from Boulanger.