discourse/plugins/chat/assets/stylesheets/mobile/chat-footer.scss

.full-page-chat {
  #main-chat-outlet.chat-view {
    display: grid;
    grid-template-rows: 1fr auto;
    grid-template-areas:
      "list"
      "footer";
  }

  .channels-list {
    grid-area: list;
    padding-bottom: 0;
  }
}

.c-footer {
  &__item {
    .c-unread-indicator,
    .c-unread-indicator.-urgent {
      margin-left: 1rem;
    }

    &.--active {
      .full-page-chat & {
        .d-icon,
        .d-button-label {
          color: var(--d-nav-color--active);
        }
      }
    }
  }
}

.has-full-page-chat div#reply-control {
  display: none;
}