By looking at the whole sefer, seems like Rambam objects to taking money for learning or teaching (Oral Torah) to keep learning pure and not use it as a source of income. Seems like he objects to direct payment for learning, not generic “tzedoka”, but Rema in YD 246:21 says – someone who is not working and supporting himself from tzedoka, so in his minds , tzedoka is same as paying. Rema further gives 2 famous kulos – first for the Rav of the city, so that people would not look down at him, and some even further – to accept willing donations for learning (this would not include Israeli taxes that are not volunteered). He then goes back to say that despite the accepted kulos, those who are able to work and learn, it is midat hasidut and present from Hashem to be able to earn an honest living and learn.
Maybe the reason Rambam does not mention tzedoka option but only payment for Torah, because he addresses it in metanot aniim, saying that everyone should try working, even as Talmid Chacham or a Kohen. He also says that it is asur to get non-Jewish welfare in public before using Jewish sources.
Overall, judging by multitudes of later sources that say this Rambam is difficult to hold by, there is a definite license to not fully follow this for those below midat hasidut. Some of Rambam’s warnings can be observed in practice in each generation to see how much one can contradict Rambam’s advice – is the Torah becoming bizayon in the eyes of multitudes? does this lead students becoming listim or doing other avonos?
this may depend on the particular community, not just esim – do simple folks see your community as takers or respect your learning? does your community force others to support or donors line up at the door?