CSS examples:
// Hide topic buttons
// Assign
#topic-footer-button-assign {
display: none;
}
// Defer
#topic-footer-button-defer {
display: none;
}
// Flag
#topic-footer-button-flag {
display: none;
}
// Bookmark
#topic-footer-button-bookmark {
display: none;
}
// Share
#topic-footer-button-share-and-invite {
display: none;
}
or
// Hide main buttons at once but Follow
#topic-footer-buttons .topic-footer-main-buttons {
display: none;
}
or
// Hide all buttons, incl. Follow
#topic-footer-buttons {
display: none;
}
To apply this code to external themes, you need to fork original Github repo, reinstall theme using your repo URL, apply this code to your repo (desktop.scss etc) commit changes and update theme in Discourse.