I would recommend using Language Transfer.

It has courses for about 10 languages. All of them are sets of MP3 files, about 10 minutes each. You can download them from soundcloud, listen via YouTube, or install the simple but very effective app.

I think you would be shocked at how natural and effective this system is. I have been using it to learn Spanish as my fifth language, and it is easily the best language acquisition system I have ever used short of living in the target country. It explicitly avoids and discourages memorization.

It's completely free, but the creator asks for donations to cover his expenses. Believe it or not, one man has created courses for French, Spanish, German, Italian, Greek, Turkish, Arabic, Swahili, and recently Japanese.

Name the language. Don't ask for a drop in replacement.

Anki?

FOSS and you can create your own decks or download those made by others.

I use Duolingo every day, seems pretty effective to me.

I'm not sure how it's a privacy nightmare. I gave them my email address for spam and a false name.

To avoid the ads, I use it via browser (firefox with ublock origin) on my phone instead of on the app.

There is a group that does studies on different apps. They look at how much time people spend using a language-learning app and how much each minute of studying adds to a standardized language test. Turns out, Rosetta Stone and LingQ are the most efficient per minute spent in those apps. If I remember correctly, both are privately held companies, which I see as a better sign than Duolingo’s public listing. I don’t know about their privacy policies, though.

rosettastone.com is something I used like 15 years ago. Kind of a desktop Duolingo or that's how I remember it.

Didn’t know that is was a privacy nightmare, would like to know more

I had Lingonaut recommended awhile ago here, but it is in early development and still doesn't support desktop use. It looks like it has apple and android support (maybe? both in alpha I think) but that isn't how I would interact.

There is Qlango which is neat because it is available on Accrescent. Haven't tried it though.

I haven't tried it yet, but I got recommended Mango for this.

Not privacy focused but read on if you want my thoughts on Duo vs Busuu. I used Duolingo back in the day but they chased me away with their complete 180 on ads (they used to advertise as no ads ever!). Duolingo was great for learning vocab but terrible for grammar in my opinion (at least eng-> german and eng-> spanish).

After bailing I didn’t use anything for awhile but I picked up Busuu a few years ago shortly after it was purchased by Chegg. They have a premium and an ad supported tier and the ad tier is terrible, it makes you have to close out at the end of each lesson to proceed past an annoying screen trying to get you to upgrade. The premium is advertised at about $70 a year but it comes down to around $50 for good sales. The monthly is a bit pricey ($10 or $12 or something).

Anyways, I really like Busuu for learning grammar. They have a flash card section for vocab that’s excellent as well but the grammar is where I saw huge improvements. The grammar is introduced in the lessons then given a strength that degrades over time until you practice it again. It tells you where your skills are weak so you can focus on a particular grammar element.

I also really like that they include regional differences in word use and regional expressions.

They recently introduced an AI speaking feature but I haven’t opted into it because I’m not comfortable with them processing my voice data. I haven’t read the privacy policy. This means skipping 1-2 lessons each unit which isn’t a big deal to me.

Hope this info is helpful to someone!

I use Lingodeer. It's pretty good.

It works as a webapp