Issue
In your website, three carriers (Three (3), Bouygues Telecom and Free) are still claimed to be in the beta phase of supporting RCS messaging.
But since the recent release of iOS 18.2 public update, these carriers can now use RCS messaging without having to register into the iOS/iPadOS beta program, making the RCS compatibility status completely inaccurate as of today. I can confirm it myself since I updated my device on iOS 18.2 and I am one of the carrier mentioned above.
Fix
• Manually modify the page (please don't, if possible) by changing one by one their RCS compatibility status.
• Revise your code that manage how the website checks* for each carrier if they supports RCS messaging.
Comment
According to some French and English articles, in order to get RCS messaging, you must update on iOS 18.2 in order to profit RCS messaging on these carriers. It is unfortunately not like an easy to go OTA update.
* Not sure if it's processed locally of if it's actually the server sending the information to the visitor of your website. And I am also not sure if it's really open source, because some developer would only make the front-end open-source rather than the back-end. But I can understand your choice.