Khan Academy offers free online learning courses, and at the time of lockdown it is very popular. As well as this, free (I say free, but there is a paid plan to remove ads) learning app Duolingo pairsvery well with Khan Academy, and I know as I am doing both. On the other hand though, Brilliant.org and Babbel offer a paid plan and a free plan, the latter of which is not very good as some courses are locked.
All of the options listed above only work if you sign up, which is a downside to people who put privacy in front of everything else (not saying that's bad). Google's trackers have been found on 75% of the top million webstes, so why wouldn't you!
Khan Academy is focused more for children in secondary school and university, but anyone can do it. My dad and me both learn there, my dad especially as he is very strict about things costing money.
Heus! Et Pater meus mihi tum etiam usum Duolingo!* My dad learns French, and I learn Latin. I've got a 10 day streak on it but my dad has been doing Duolingo for 761 days!
So, which one should you get? Pay for Brilliant or Babbel or get Khan Academy for free? I guess the only thing we can do to decide is ask you to comment below!
*Translation: Whoa! Me and my dad both use Duolingo too!
Free is always better