The links you provide have to do with giving up one's life to prevent committing a sin. I'll answer according to your question on rabbinical violations that carry a death penalty.
There is a baraita found throughout the Talmud (such as Ber. 4b) which states:
וכל העובר על דברי חכמים חייב מיתה
Anyone who transgresses the pronouncements of the Sages is liable to
receive the death penalty
This statement does not mean that the courts can impose the death penalty on people who commit such transgressions. Most commentators understand the baraita as a way of underscoring the seriousness of rabbinical pronouncements, to the extent that one is worthy of death if transgressing one.
That said, there are no rabbinical laws punishable by karet. The list of sins punishable by karet can be found in the talmudic tractate devoted to this subject (Keritot 2a), and they all derive from the Torah.
There is a potential caveat, however, that deserves mention. The Rambam appears to indicate that the courts could strike a sinner to death for repeating a rabbinic law:
אסרו חכמים לאכול מצה בערב הפסח כדי שיהיה היכר לאכילתה בערב. ומי שאכל מצה בערב הפסח מכין אותו מכת מרדות עד שתצא נפשו
The Sages forbade a person from eating matzah on Pesach eve, in order for there to be a distinction between [partaking of it as food] and eating it on the evening [of the fifteen as a mitzvah.] Whoever eats matzah on Pesach eve is given "stripes for rebellion" until his soul expires. (Mishneh Torah, Chametz uMatzah 6:12).
Many commentators have used the final clause ("until his soul expires") to understand the extent of rabbinical authority. The Ran, for example, uses Rambam's point to emphasize the first point I mentioned, borrowing language from the Mishnah (San. 11:3):
ולפי דבריהם יש בזה חומר בדברי סופרים יותר מדברי תורה
These words prove that the law is more severe with respect to the words of the Sages than to the words of the Torah. (Ran on Rif, Ketubot 16b)
It is crucial to note, however, that the most authoritative manuscripts of the Mishneh Torah do not have "until his soul expires" in the text. It is a later addition not from the Rambam, and many contemporary publications of the Mishneh Torah do not include it.