Android 7 breaks certificates on Samsung Browser and in Whatsapp

On a Samsung S6 Plus Edge running on Android 7, certain security certificates will break since September 2021: the workaround which Let's Encrypt implemented doesn't seem to work in Samsung Internet. I get the standard "Back to safety" screen. For browsing this is not an issue, I can use firefox. But I have an issue with WhatsApp: it will not load preview images from such websites, as probably it routes such requests through Samsung Internet or some samsung API. Changing the default browser doesn't help. Is there a workaround for this which doesn't involve rooting the device ? I've seen this answer , but it looks like I can't install certificates manually if the device isn't rooted.