(This got long; sorry!)
Firstly, I was going to recommend Anki but I can see @Aaron_Antcliff has beaten me to it. Especially if you are learning anything that involves some degree of rote memorisation (which is most everything, really). I use it mainly for Spanish vocabulary and memorising my students’ names these days, but have used it in other academic studies previously and I keep thinking I should expand this to other areas.
As far as software for learning that kind of information is concerned, Anki is killer. I’ve been using it for longer than I can remember (at least 7 years at this point, but probably longer).
There are a couple of points I would highlight about it because it is just such a powerful tool in my opinion:
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They key is spaced repetition i.e. the idea is that Anki will show you things just before you forget them, and the easier something is for you to remember the longer the time before it will show again. I know there are other apps that do this but I haven’t really played with any of them so couldn’t tell you how they compare.
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You can customise the fields and the cards that are generated (beyond just front/back flashcards) and this is HUGE. For example I have a Spanish irregular conjugations deck. Rather than having to create a note for each conjugation, I have a note type called ‘verb’ or something where I enter all the conjugations in one place. Then I have set up templates in Anki that generate all the possible combinations of cards I want.
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If there is specific, structured data you want to enter, there are a couple of options to consider.
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First, you can import something like a csv file (I think there are some other options too) so anything you can get into that format you can import in bulk. I have just finished off (and intent to write up/share at some point) a Keyboard Maestro macro where I can enter the infinitive form of a verb, it will get the HTML of a Spanish dictionary website, grab all of the conjugations (including a ‘span’ that includes the irregular part of the conjugation), and add them into a text file that I can import straight into Anki. Not only is it WAY faster (as in, I’ll actually bother to enter them now) but also a lot more accurate, which is important in a context like this. (Recently discovered that the word I thought meant ‘slop’ in fact meant ‘slope’, for example!)
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Second, with the note that I haven’t played with this at all, there is a URL scheme available for adding cards so if you want to streamline creation of cards with Shortcuts or similar that would be a possibility, i believe.
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Some items won’t be able to be created “automatically” and that’s okay, and sometimes good. I think the process of taking some information, understanding it well enough to synthesise it/distill it down into a question that you can answer (preferably in a way that is either right or not) is really valuable for the learning process in and of itself.
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There are heaps of add-ons which are well-worth browsing. For example:
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For languages, there is a text-to-speech extension so you get audio. Good for reinforcement, but I am, for example, using templates as described above in conjunction with this using templates above I create “audio-only” cards out of my existing notes so I can’t rely on just reading the words.
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There is an “image occlusion” plug-in which is pretty cool (though I don’t have a use for it currently). It basically lets you blank out different parts of pictures to use as cards.
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I highly recommend checking out the Anki manual to get some ideas of the kinds of things you can do, including the above. In addition, there are many posts online about the best ways to go about creating cards which may be worth a look.
Outside of Anki, I don’t really have many “learning” tools that I can think of (other than those that are specific to a particular subject area, for example things like Duolingo). But I would say in terms of getting myself to actually do these things, what is working for me at the moment is:
- A daily repeating task in OmniFocus that automatically shows in my “Do” perspective, because this is where I will see it.
- A note on the OF task with a link to a Siri Shortcut which opens whatever I need to do the task (Anki, or Duolingo, for example), starts a time-tracking timer, and marks the task as done in Streaks.
This is for smaller repeating habits that I want to do regularly, rather than big blocks of time spent learning. I think it works because I have a limited “Do” list each day that I want to try and check things off of, I have the link right there so there is minimum resistance to tapping it, and once I have done so it’s been marked as done so I’m basically guilted into doing it at that point. Streaks is new to the setup but I think it helps because the actual “streak” of days completed motivates me to complete the action—if I only use Omnifocus, where I know that if it’s getting towards the end of the day and I check that task off, it’s only going to come back tomorrow, so it’s easy to skip it. Streaks just adds a bit more pressure. 
(Hopefully that is more coherent than it felt while writing it, haha.)
I have also created a “Today I Learnt” journal in Day One with a similar prompt to the above). I like the idea of this but admittedly haven’t made great use of it yet so I’m not sure how it will pan out.
Sorry for the length and the Anki-evangelism but this was what came to mind when I saw your post.