There's 2 main ways I'd consider:
One of them is peer to peer or over the counter where you'd do multiple smaller trades.
The other would be to buy a stablecoin/stock derivative and wait with that until you find a good time to sell.
There are a few companies that'll allow you to convert crypto to stocks positions and a few that'll hold cash on your behalf from their own issued currency (the main one I can think of is etoro but it might not be the only one - primexbt, bybit and binance also would allow you to take out a 1x long on stocks or the dollar for your crypto.
De-risking by going into a stablecoin is an idea
Let's say you have a large amount of BTC and you want to spend it / invest it / transform it in fiat but you do not want the BTC to be traced to exchanges or to you, how would you do it ?
It's not for me, it's to further my understanding of the space.
I haven't been in such a situation before so it's kinda hard to give a direct answer but in the past, I've seen people using Bitcoin mixers as a way of getting around the privacy issues that abound with using other methods like P2P or even going straight to an exchange to do it. Another option would be to transfer the BTC into a wrapped BTC you can use on decentralized exchange which you can then change to an altcoin and then send to a different wallet before finding moving it to wherever you want. Bitcoin mixers seems like the most effective that's why govt has been trying to crack down on them recently.
Mixers are definitely a tool to consider.
I found an article about the subject :
https://www.vice.com/en/article/7xdzqa/criminals-are-racing-to-cash-out-their-bitcoin-heres-how-theyre-doing-itThey are talking about the option to buy prepaid debit cards, you need an address to receive it which will be a point of contact between your bictoins and you, and you will probably pay up to 10% in fees and would probably not be able to cash out more than 500$ or 1000$ per card.
I guess there are options available on the dark net. Finding a dark OTC to cash out large sums is very risky bc you could get scam.
P2P is the best choice if you want to convert your bitcoin into fiat. Find someone that is reputable or someone you know that buys a lot of bitcoin in exchange of fiat. This is also the main problem of people who holds a huge value of cryptocurrency. For me if I want to convert it into fiat, I would not do it in one day. I would divide it into an amount that will not alert the bank make them investigate your account. If you managed to convert it into fiat without being traced then the government found out you bought some assets that cost very expensive then you would be suspicious to them. As long as you got it legally, I think there is nothing you should be scared of.
The legal route is the safest.