I noticed the iframe is not supported inside notification node when the node is in OK/Cancel dialog mode.
All other modes (Top right...) seem fine.
Do you experience the same?
[{"id":"70defbae.9bcd64","type":"ui_toast","z":"7e861a7c.4452b4","position":"dialog","displayTime":"3","highlight":"","outputs":1,"ok":"OK","cancel":"","topic":"","name":"","x":1030,"y":200,"wires":[[]]},{"id":"264c3fa5.434d6","type":"ui_button","z":"7e861a7c.4452b4","name":"","group":"79013da6.5bad14","order":0,"width":0,"height":0,"passthru":false,"label":"button","tooltip":"","color":"","bgcolor":"","icon":"","payload":"","payloadType":"str","topic":"","x":670,"y":200,"wires":[["ffdbac93.2d50c"]]},{"id":"ffdbac93.2d50c","type":"template","z":"7e861a7c.4452b4","name":"","field":"payload","fieldType":"msg","format":"html","syntax":"mustache","template":"<iframe src=\"https://www.nasa.gov/\">\n Your browser does not support iframes.\n</iframe>\n","output":"str","x":820,"y":200,"wires":[["70defbae.9bcd64","e34f5cc4.d613a"]]},{"id":"e34f5cc4.d613a","type":"ui_toast","z":"7e861a7c.4452b4","position":"top right","displayTime":"3","highlight":"","outputs":0,"ok":"OK","cancel":"NO","topic":"","name":"","x":1050,"y":240,"wires":[]},{"id":"79013da6.5bad14","type":"ui_group","z":"","name":"Default","tab":"9f07378d.44b478","disp":true,"width":"6","collapse":false},{"id":"9f07378d.44b478","type":"ui_tab","z":"","name":"Home","icon":"fa-bath","order":1,"disabled":false,"hidden":false}]
