Sorry, but your suggestion doesn't work for me:((
1. Update fix from https://github.com/unaio/una/issues/1158 applayed
2. File MyIframe from GG explanation here was added
3. In working inc/utils.inc.php file at 525 line added a fix (here in BOLD)
$oConfig->set('Filter.Custom', array (new HTMLPurifier_Filter_MyIframe(), new HTMLPurifier_Filter_LocalMovie(), (new HTMLPurifier_Filter_YouTube(), new HTMLPurifier_Filter_YoutubeIframe(), new HTMLPurifier_Filter_AddBxLinksClass()));
4. New inc/utils.inc.php file crashes the site. when I put the old inc/utils.inc.php - all working fine. Which means, imho, that inc/utils.inc.php can't stand this change.
5. It do works before 9.6 update, so somewhere is some change, there is no other explanation. The point is - what change and how to get custom filter work again?
Thanx in advance