Investigating activity summary email dark mode issues

Thanks for the details!

As a quick workaround, I added this CSS to the Emails settings:

@media (prefers-color-scheme: dark) {
    body > div > table > tbody > tr > td > table[dm="header"] {
        background: #c89f4c !important;
    }
}

It make the header background lighter and my Logo is now displayed properly (in preview at least).