Everywhere. A few examples:
Product News on the Aqara Shop site:
The Radiator Thermostat W600 combines smart automation with energy savings. Compatible with popular valve types (RA, RAV, RAVL, Caleffi, Giacomini, M28×1.5)
(Aqara Showcases New Smart Home Innovations at IFA 2025 - Aqara UK Shop)
Trial offer from Aqara in this forum:
Confirmation that your setup supports the Radiator Thermostat W600: compatible with valves M28×1.5mm
(【Exclusive Trial】Aqara Radiator Thermostat W600 – Be the First to Try)
The same invitation, with the same M28 reference, also appears on X.
Homekit News:
It works with RA, RAV, RAVL, Caleffi, Giacomini, and M28×1.5 valves
(Aqara Unveils New Devices Ahead of IFA 2025)