if you want to add this to your own nginx setup:

map $http_user_agent $brnotice {
    default         '</head>';
    ~*Chrome        '<link rel="stylesheet" href="https://maple.pet/notice.css"></head><div class="impnotice">You are using an unsupported browser. Please visit <a href="https://getfirefox.com">this website</a> to upgrade your browser.</div>';
}

server {
[...]
    sub_filter '</head>' $brnotice;
    sub_filter_once on;
}```