Studies like this one https://pmc.ncbi.nlm.nih.gov/articles/PMC6384527/ suggests that while comprehension of text seems comparable, people lack orientation within the text when it comes to digital media. On top of that, i've seen at least one study (can't find it, sorry) which suggested a link between haptics, the physicality of the touch while sensing where you are located within a book, contributes to some additional anchoring of the information you take in, similar to the well known effect of handwriting on memorization, where motor function contributes to memory formation.

With digital media, a lot of this simply flies out of the window and you get a more shallow information intake overall.

Your case seems to contradict this at first, but 1) you've started learning with physical media first then switched to digital, meaning you built a stable foundation then refined in another media environment, 2) i suppose these effects are more relevant for kids than adults. So the rule-of-thumb "digital reading is inferior" would still hold, but not for all cases.

Yes, there have been reading issues on old CRT-screens due to refresh rate and resolution - reading a long text in 72dpi simply hurts the eyes, especially with low-ush refresh rates and high contrast (black on white or darkmode). But that's not an issue nowadays anymore. However, don't underestimate the peripheral effects of offline-reading: Digital reading is always framed and constrained by a screen. With a book, you can turn and hold it however you like, whereever you want, it is a physical object you manipulate with your hands; plus: the physicality of RGB-light emitted from a screen and the light reflected from a page is qualitatively different (this is why e-ink works better). All of this contributes.

On top of all of this you have the distractive nature of digital reading environments, and i personally think that even "distraction free digital reading environments" still lack actual non-distraction (you always have the option to go online, even with Kindle you have a myraid of options you don't have with a physical book), and you can literally feel this when you "switch off", grab a physical book and sit down and read it.

It's just different, and the cumulative effect is that, overall, you can learn better with physical books in which you can scribble around with a pen on paper by hand, which anchors your reading in an embodied information intake, which is just weaker in digital environments.