There's a disagreement recorded in the Mishna, Zevachim 13:6, regarding the Sukkot water libation. R' El'azar includes this ceremony in the list of Temple activities that are prohibited by the Torah to perform outside the Temple, in this case, specifically on Sukkot. His position opposes the default position in the mishna (the tana kama), which does not include the water libation in this prohibition.
R' Ovadia MiBartenura comments:
דסבר ניסוך המים בחג דאורייתא היא הלכך מחייב עלה בחוץ ואין הלכה כר״א בכולה מתניתין ונסוך המים בחג לאו דאורייתא היא אלא הלכה למשה מסיני
... for he holds that the water libation of Sukkot is from the Torah, so he says that one is liable for performing it outside [the Temple]. And the accepted law does not follow R' El'azar throughout this mishna. And the water libation is not from the Torah, but a halacha leMoshe miSinai.
I was curious how the distinction between the water libation's source being in the [Written] Torah and being a halacha leMoshe miSinai, which are both kinds of Divine legislation, would bear on whether or not the prohibition of outside services would apply to it, as R' Ovadia seems to imply, so I looked at the Gemara on this Mishna (Zevachim 110b). There, to resolve a technical point in R' El'azar's position, the Gemara concludes that he must hold that the source of the water libation is a halacha leMoshe miSinai. The Gemara doesn't appear to address the tana kama's position regarding the water libation's source. From the back-and-forth in the Gemara, it seems that if its source was derived from the Written Torah, as cited there to R' Akiva, the prohibition of doing it outside the Temple would apply even more widely.
So now, I don't understand R' Ovadia's last line. It seems to imply that the position that the water libation is a halacha leMoshe miSinai is the accepted law, in contradistinction to R' El'azar, who holds that it's "from the Torah." If this reading of him is correct, it directly contradicts the Gemara, which concludes that R' El'azar must hold that it's a halacha leMoshe miSinai. Is this the right reading of R' Ovadia? If so, how does he understand the Gemara?
Or, we could read R' Ovadia as ascribing this statement about halacha leMoshe miSinai specifically to R' El'azar. I think this is a tortured reading of this comment, though it's consistent with the Gemara. In this case, why throw this line in at all? Unless you get to the technical point discussed in the Gemara, which is brought up neither in our mishna nor in R' Ovadia's commentary on it, this distinction doesn't make a difference to the prohibition the mishna's discussing.
Or, we could read R' Ovadia as concluding that R' Ela'zar and the tana kama agree that the water libation is a halacha leMoshe miSinai, though they disagree about whether the prohibition of doing it outside applies. If so, on what basis does the tana kama disagree? And again, why throw this line in at all?
Finally, what does the tana kama hold regarding the source of the water libation? It would be easiest to say that the tana kama holds that it's Rabbinic legislation, so the Torah prohibition of outside performance can't apply. This seems to be implied in the first part of R' Ovadia's comment. If so, is this corroborated somewhere else in the Mishna or Gemara? (Rashi comments on the Gemara's conclusion that "everyone holds that it's from the Torah," but perhaps that just means everyone mentioned in the discussion in the Gemara - R' El'azar and R' Akiva - and not truly everyone, such as our tana kama.)