Via custom CSS you can do this
.page-topic .pagination-block {
display: none !important;
}
In a theme you can change navigator.tpl and remove d-lg-block
https://github.com/NodeBB/nodebb-theme-harmony/blob/73b6431f56990778a81e6948cc1e33d5458ddc14/templates/partials/topic/navigator.tpl#L1