Something similar happened in Argentina. +60% interest rates with 45% "official" inflation and a constant exchange rate with the USD. I was able to get returns of more then 60% in USD because I sold my mutual funds and bought dollars before they chose to devaluate the peso.

The problem was they allowed the currency to devaluate in a matter of days. People with CDs or mutual funds with long withdrawal time lost a lot of money. I'm talking about going from 18pesos = 1 usd to 36 pesos = 1 usd in something like one week.

You can actually see how the lira is losing against the usd since 2008.

While this is true, as other have said, there is a high chance that inflation is higher than what is shown (although i doubt that this is as much as 50%). But another issue is that the government as been trying to fix its own deficit, due to the lasting crisis, by adding taxes to almost anything. You now pay taxes for buying a phone (second hand or not), for buying gold, for buying a car (fairly common but it is much higher now), taxes on alcohol are now at an all time high, ... And in general, foreign good cost a lot more. As an example, some of my acquaintance in Turkey are asking me to buy some electronic device (like computer, playstation, ...) here in France and they will send me the money, because the price of those goods in France is overall cheaper, even when you include the cost of converting lira to euro.

Now, this should in fact raise the inflation, but it seems that they indeed chose a way to compute inflation that doesn't show this effect as much.

As a Turkish citizen I can say that the real inflation is much higher than 17% but they are trying to make it look lower by changing the formula constantly so they don't have to raise government employee's salaries so much. I would say the real inflation is closer to 50%.

I didn't do much research so lets assume you are right but at the same time I hope you do not confuse asset prices with consumer prices. The PCI in the USA is correct and people still cry that it is manipulated.

If the government is under reporting inflation that is a problem with the government. The obvious solution is to just report correct inflation. Once the government has reported correct inflation numbers the Turkish central bank must raise interest payments and that would mean at least 52% interest. The fundamental problem doesn't change though. People are still fleeing the influence of the Turkish government, not the currency. You need to trust the government and the government must eliminate internal corruption.

50% per year? How and where are you storing your savings in this circumstance?

The value of the Lira has plummeted far far more than 19%. That's exactly why people are trying to get their money out of Turkey.

...which is exactly why they're turning to crypto.

...which is exactly why Turkey enacting currency export controls, like banning crypto.