Actually Papyrus Rylans 458 has lacunae where either YHWH or KYRIOS would be found. The Wikipedia entry for this is clumsily written, if that is what you are relying upon:
The manuscript has been used in discussions about the Tetragrammaton, although there are actually blank spaces in the places where some scholars such as C. H. Roberts believe that it contained letters.[3] According to Paul E. Kahle, the Tetragrammaton must have been written in the manuscript where these breaks or blank spaces appear.[4]
The text is not extant in the places where the divine name would appear, so experts have divided over what would have originally stood there. Paul Kahle for example was confident that the Tetragrammaton was used in the text. In truth the text simply doesn't survive where it would need to in order to tell us one way or the other. See section 1 here that explains:
http://digidownload.libero.it/domingo7/howard.pdf
You can examine the whole thing to see that neither YHWH or KYRIOS is part of the preserved text:
https://en.m.wikipedia.org/wiki/Papyrus_Rylands_458#/media/File%3AP._Rylands_458.jpg
The author of the Wikipedia entry apparently equates "blank spaces" with lacunae, which is confusing for people familiar with the later manuscript of Genesis (PBerlin 17213) that reportedly has blank spaces where the divine name should appear. (Although this is disputed by Emanuel Tov) This manuscript dates from the third century CE and represents a relatively late development in the treatment of the divine name.
All the earliest extant copies of the LXX used either YHWH or IAW. Copies using substitutes do not appear until the second century CE. The fragments of the LXX from the first century and earlier use YHWH or IAW. There are no fragments from this early period that use KYRIOS. Or if there are could you point them out?