Does one have to be a practicing Jew for their antisemitic experiences to be valid, or are descendants that don't practice not 'really' Jewish enough to experience antisemitism.
Any kind of Jew can experience antisemitism. Practicing, non-practicing, matrilineal descent, patrilineal descent, convert, Ashkenazi, Beta Israel, Reform, Hasidic, and so on.
Antisemites (generally) don’t split hairs over how observant a Jew is or ask themselves “well, does she go to synagogue on Shabbat?” or “does he daven daily?” before they choose to target that person. All they care about is that the person is, to their knowledge, Jewish or a “Jew-sympathizer.” Observance of the halakhah just doesn’t tend to be the determining factor, and gentiles are often ignorant of halakha and Rabbinic teachings anyway.
That’s not to say that observant Jews, particularly those who wear traditional garb or things like kippot, cannot be easier targets for antisemites. People who are visibly Jewish can be targeted for antisemitism without ever having to say “yes, I am Jewish” or reveal a very Jewish surname. In addition, people who live in Jewish communities or are associated with Jewish organizations can be more easily targeted just out of the fact that it’s easier to tell that they are Jewish.
It’s worth mentioning that Jews who are not observant can also be visibly Jewish, whether because of genetics or due to wearing items such as Magen David necklaces, and can also be involved in Jewish organizations and the like. Religious observances isn’t the determining factor of “how Jewish” a person is, and how a person sees themself and presents themself to the world is very important.