Vājasaneyi saṃhitā; Madhyandina and Kāṇva schools.
Index only — text still opening
In the Vājasaneyi recension the Īśāvāsya Upaniṣad is the last chapter of the saṃhitā itself. That is why the Īśā slice in this library cites Śukla Yajurveda numbering.
Ashram guide
Answers from this website, including Brahmexa website solutions. Not Sri Meenananda Tirthanath. It will not give diksha; it will point you to the Diksha page.