something like this should do the trick and might be overkill, but give it a try…
add_filter('sph_setup_forum', 'my_mobile_check');
function my_mobile_check() {
global $spMobile, $spDevice;
remove_filter('sph_topic_editor_toolbar_buttons', 'sp_plupload_editor_button', 5, 4);
remove_filter('sph_post_editor_toolbar_buttons', 'sp_plupload_editor_button', 5, 4);
remove_filter('sph_pm_editor_toolbar_buttons', 'sp_plupload_pm_editor_button', 5, 2);
remove_filter('sph_topic_editor_footer_top', 'sp_plupload_uploader_form', 10, 3);
remove_filter('sph_post_editor_footer_top', 'sp_plupload_uploader_form', 10, 3);
remove_filter('sph_post_edit_footer_top', 'sp_plupload_uploader_edit_form', 10, 4);
remove_filter('sph_pm_editor_toolbar', 'sp_plupload_uploader_pm_form', 10, 2);
remove_filter('sph_SignaturesFormBottom', 'sp_plupload_uploader_sig_form', 10, 2);
}
now you will want to add in some checks before doing the ‘remove’… $spMobile will be true for tablets or phones… or you can check $spDevice which could be ‘desktop’, ‘tablet’ or ‘phone’…