I think it's quite frecuently meant to convey the literal act. If I search for the word in the news, I get lots of examples of it (this is just the first: https://www.businessinsider.com/coronavirus-trump-retweeted-...).

Obviously, if you are using it in an internet forum you're probably not literally facepalming, just as if you use "lol" you're not laughing out loud, but even in these cases, I don't think that means that you can entirely decouple the word from the gesture. At least for me, when I read the word, what I imagine is someone facepalming. There are several other ways to express resigned frustration (a sigh, a shake of the head) but they are not the same even if they are ways of expressing the same.