Status of the descendants of Yarcha
In Ki Tetzeh it says (Devarim 23:8-9):
"You shall not abhor an Egyptian, for you were a stranger in his land. Children born to them may be admitted into the congregation of the LORD in the third generation."
In Hilchot Issurei Biah 13:11-12 it says:
"Just as we circumcise and immerse converts; so, too, we circumcise and immerse servants which are acquired from the gentiles for the sake of servitude...When a servant is freed, he must immerse himself a second timein the presence of three men during the day, for through this act, his conversion is completed and [his status] becomes that of a Jew..."
"Sheshan had no sons, only daughters; Sheshan had an Egyptian slave, whose name was Jarha. So Sheshan gave his daughter in marriage to Jarha his slave; and she bore him Attai."
According to Rashi and Radak, Chazal say (though unclear where exactly, as explained here) that one of Yarcha's descendants was Yishmael ben Netanyah (likely based on the fact that one of Yarcha's descendants was called Elishama, the same as Yishmael's grandfather), who went on to murder Gedaliyahu ben Achikam.
As Yarcha entered kahal Hashem immediately after finalizing his conversion (when he was freed by Sheshan)1, contrary to the halacha of Egyptian converts, I was wondering what was the status of his descendants: Are they mamzerim? Something else2? Or maybe it's a sin that only has ramifications for the individual sinner (Yarcha, in this case)? Or perhaps there was some sort of heter (such as when Rabbi Eliezer freed his slave for a minyan)?
1 While it's not completely pshat that Sheshan freed Yarcha, it seems that this is most likely what happened, and that is how Rashi puts it: "מכאן אמרו בתך בגרה שחרר עבדך ותנהו לה" - "from here they said, your daughter has reached adulthood, free your slave and give her to him."
2 Rashi, for example, refers to Attai, son of Yarcha, as "Attai Hamitzri". Generally in Tanach, to my knowledge, descendants of converts aren't themselves referred by their parents' original nationality. For example, Rechav'am who was the son of Na'amah Haamonit isn't himself called an Amoni; Amasa who was the son of Yeter Hayishmaeli isn't himself called a Yishmaeli, and so forth.