When I put
ulysses bloom circumcised into Google, the top result was this Jstor page for the academic article Erwin R. Steinberg, "James Joyce and the Critics Notwithstanding, Leopold Bloom Is Not Jewish", Journal of Modern Literature 9(1) (1981), pp. 27-49. This article says:
At birth, Bloom was not circumcised, for, in the Nausicaa episode, after he masturbates, Joyce has him think, "Stuck. Well the foreskin is not back. Better detach" (373). In this connection we might note that Joyce was not unaware that male Jews are circumcised. He has Stephen discourse leamedly on Jesus' circumcision (703), and in Circe, he brings onstage a group of Jews who appear "in sackcloth and ashes, . . . by the wailing wall" and to whom he twice refers as "the Circumcised".
I checked the full text of Ulysses and confirmed that the quote from Chapter 13 "Nausicaa" is indeed as Steinberg has it:
As God made them he matched them. Sometimes children turn out well enough. Twice nought makes one. Or old rich chap of seventy and blushing bride. Marry in May and repent in December. This wet is very unpleasant. Stuck. Well the foreskin is not back. Better detach.
Other hand a sixfooter with a wifey up to his watchpocket. Long and the short of it. Big he and little she. Very strange about my watch. Wristwatches are always going wrong.
Foreskin, therefore no circumcision. No need to go into any more detail than that.