As Rambam says in Hil. Isurei Biah Ch. 12, there are issurei dirabanan in addition to issurei dioraissa for having sexual contact with a non-Jew. Our Gemara is one source, Malkin al lo tovah hashmua. Also, see Brachos 58a that Rav Sheila gave malkos to someone who was boel mitzris (or Aramis to girsa of Magid Mishna), and also see Taanis 24b, there was a certain man who was boel kusis and received malkos.
I would like to quote the Otzar Haposkim 5:12, os 75 about Malkos Dirabanan.
See Beer Heitev 12 - these makas mardos are 13 malkos, Maharai, Rashi end of Ki Tetzei. Magen Avraham O"C 496 writes frim Rambam it does not seem that way. See Rashi Chulin 141b who writes makas mardus has no set amount, until he accepts upon himself.
And Pri Chadash O"C 471 os 2 brings Rambam Hil. Chameitz Umatzah 6:12 that makas mardus is until his soul departs. Ran Kesuvis, beginning of Chapter 4 writes that it appears this way from the Aruch, and to them they are stricter than makos dioraissa [which are 39], and there is support from this fro taanis 24 that someone was baal kusis and Rav gave him malkos and he died. Teshuvos Rivash 90 writes that in no situation where one transgresses the words of the chachamim gets malkos until his soul departs, and he did not remember that the Rambam does hold this way. Ran brings in the name of Ramah that makas mardus is estimated [as to how many he can receive, just like makos dioraissa) and to be more lenient than makos dioraissa (and this is also Rivash's opinion) and his words appear [to be correct]. However, certainly for makas mardus for a continuing sin we lash him until his soul departs or he accepts the words of the chachamim, these are the words of the Ran. And this is Rashi's opinion at the end of Chulin: Makas mardus is hitting and reproach that he will not act like this regularly and there is no set amount [of lashes,] unless he accepts [the words of chachamim]. He implies that if he already transgressed, we hit him according to Beis Din's estimation and the severity of his sin. And Tosfos holds is like Rivash wrote in their name that even makas mardus have the same number of lashes as makos dioraissa but they're not as hard (see Tosfos Nazir 20b s.v. Ri) and there is support for this from Kiddushin 28 "one who calls his friend 'mamzer' gets 40 lashes." but Rashi Yevamos 52 where it says "but it says in a braissa he gets malkso" writes there are only 40 lashes for makos dioraissa, and he answers this isn't 40 lashes, rather it's makas mardus dirabanan, and the opinion of Rashi and Ran is the main opinion.
Gra C"M 27:12 on that which the Shulchan Aruch writes the judges wanted to lash him makas mardus the lash as many as they see fit, writes this is makas mardus to Rambam, as many as the judges see fit, and there in Yalkut he refers to Tosefta Makkos ch. 3 that for Malkos they evaluate him and makas mardus isn't like that, rather they lash him until he accepts it or his soul departs, and this is for something in the future, but for something already done it is like Rambam.
Api Zitri seif katan 19 after bringing the argument between Rambam and Ramah & Tosfos writes to this the opinion of Maharai in Beer Heitev is a daas yachid.
But Shiltei Giborim on Mordechai Bava Basra chapter Mi Shemeis os 1 writes that makas mardus is hitting & reproach, Rabbeinu Tam says this is 13 lashes which is a third of the makos in the Torah, for so did chachamim decree for one who transgresses on their words on a matter which cannot be fixed, but for something that can be fixed like Lulav on the second day they lash him until his soul departs. Tashbatz Volume 2 Siman 51 writes that Rashi in Yevamos perek gimmel (maybe he means perek r"g [Rabban Gamliel]) says that makas mardus are 13 lashes and no more, maybe Rashi Chulin...see Tashbatz. And see Sefer Amudei Eish to R' Yisrael Eisenstein, kunteros makal chavalim os gimmel who at length brings proofs that the amount of makas mardos is 40.