I will like to point that Bitcoin decentralization is different from financial privacy.
Bitcoin being decentralised means no central authority controls bitcoin protocol
Anyone can hold their own private key without permission or make transactions while relying on a third party.

There are decentralized exchanges like Bisq
It doesnt have to be a centralised exchange
You can even try an exchanger like peach bitcoin though there's a limit before kyc is requested.
There are other ways you can work on your privacy like avoiding address reuse and not disclosing your data online.

@OP if you want to purchase an item from a centralized institution, it would be hard to apply the Bitcoin decentralization.  First, you are using a centralized platform, all transactions after that will be considered centralized because its foundation is based on a centralized institution, even if you pay for your purchase directly with Bitcoin, the transaction is recorded by the centralized entity.

I think you need to purchase an item directly from the seller and not use a centralized e-commerce platform.   This way the Bitcoin you send goes directly to the seller's wallet, and you do not have to register or undergo KYC on a centralized platform.  Any information can be communicated through a private channel, like a direct message between the buyer and the seller outside a centralized e-commerce platform. This way, no third-party centralized entity is holding the record of that trade.

Well maybe you kind of miss understood OP. I think he’s just worried and trying to find A way to spend his bitcoin without linking it to any centralised exchange that will require KYC because he doesn’t want his identity linked to a those bitcoin transactions. And you know frequently transactions from a particular address to an exchange could literally mean he owns that address. However I understand your point and example of receiving money from a signature campaign manager clearly but I think he’s only concerned about his privacy here.

I think using those instant swap that doesn’t require KYC to send those bitcoins to an exchange that might require KYC should solve his problem.  And from there he can proceed with his p2p. This way it break the link between the  bitcoin  address and the identity on the exchange.

Don't you even with this methods you mentioned, you can still be easily tracked if they really want to track you ?
Just stay out of trouble at all cost
And I would have suggested using mixers but why on earth will I have to mix every of my coin for everytime I want to trade and most of these mixers have high deposit limits so for those who want to mix lower amounts might not be favored.

The issue with spending bitcoin directly and correctly for its purpose is becoming a major issue and should be of concern to everyone

The part I marked is pretty confusing. Is it me who's having trouble understanding it, or were you drunk when you wrote it?

And actually, centralized exchanges aren't the only way to buy or trade your Bitcoin. There are still options like decentralized exchanges that don't require KYC, or you can go P2P with someone else through forums or other platforms.

Just for an information, Bitcoin users are not Decentralized rather, it is the Bitcoin network that is Decentralized.
The exchange platforms are extremely regulated by the authorities and therefore demands users from uploading their KYCs and where you have revealed your identity, the authorities automatically takes control over your funds.

To enjoy Decentralization in the crypto space, you must use the non custodian Wallets that gives you total control of your funds whereas, you have your private keys under your custodian.

Also know that Decentralization in the industry is different from keeping anonymity while Bitcoin and crypto transactions is pseudonymous.

There are currently a few ways to acquire Bitcoin without submitting personal info to anyone. Even on Bisq you have to provide your bank account information to your trading partner - they can then see who you are once you sent them money. And if you buy with cash, the counterparty sees your face - it's still a good method but in theory they could take a photo from you and search you.

The original way to get Bitcoin totally without intermediaries was to buy mining hardware and mine. But this is very complicated already since ca. 2013 as the hashrate is far too high for most "domestic" miners. You may try this method though with altcoins, or if you have access to almost free energy (e.g. solar, wind, flare gas etc.).

An alternative way is to acquire Bitcoin selling storage space. This works with some altcoins like Siacoin, or Storj.

The nice thing is: once you have a decentralized cryptocurrency in your hands, you can use totally trustless and decentralized techniques - mainly atomic swaps - to exchange them to Bitcoin.

It's way more compllicated to sell Bitcoin without providing personal data. With P2P exchanges you also provide bank account data, so cash is one of the few good options. But there's another way: you can simply spend the Bitcoin. In many cases merchants don't request personal information. And if you buy physical items you can use a friend's home address for the good to be delivered.

That's your first mistake, using CEX. If you really don't want your identity to be linked or ever going through KYC process, simply use P2P.

To keep your identity secure you gotta be creative in the decentralized blockchain space.

There is platform specifically made for this like others have mentioned like Bisq, but it isn't the only route though it's the highly recommended route.

Anyway, when I say you gotta be creative I'm not kidding, beside P2P you can actually swap your Bitcoin to stablecoin using bridges like throchain and then use no KYC crypto debit card and make it spendable anywhere.

No KYC crypto debit card is frequently talked about in here https://bitcointalk.org/index.php?board=85.0, the only thing you should keep in mind is the fee, term of service, etc.

Of course, this will sever your connection to those coins, but the blockchain will show that the coins moved from address #1 (the user) to address #2 (the exchange). And this is where an interesting point arises: what if, later on, the coins are moved from that exchange to another wallet, one that ends up being used for criminal activity? In reality, the user would have no involvement in this, but an investigation could still lead back to them via address #1 (provided that a link between the user and that address #1 has been established).

At this point, you might receive bitcoin at your address (coming from an exchange service) that are of unknown origin. You have no way of knowing who held them previously, and it is entirely possible that they were linked to the criminal activities of one of their former owners. Once these assets arrive at your address, you could (in the event of an investigation) become a suspect, and your address would likely come under close scrutiny. Furthermore, if you were to subsequently exchange these assets for local currency, for instance, by transferring funds to a bank card via an exchange service that performs KYC checks, you could easily be tracked down (should authorities choose to do so).

Similar risks arise when using mixers. It is unknown what funds you will receive after the exchange.

But how will they find out someone’s identity and place of residence in order to rob them?

The problem, however, is that users have no way of knowing which addresses were involved in criminal activity, nor can they tell whether the assets (sat.) arriving at their own addresses are "clean". In theory, every single bitcoin could potentially fall under suspicion. The user themselves might not be involved in any crimes, but their bitcoin could have been used (in the past) for such activities. It’s unlikely that anyone would want to go through the trouble of having to prove their innocence later on.

Oh, those pink unachievable dreams. Perhaps it’s time to learn to take a sober look at current trends, as shaped by the regulator, and forecast the future of bitcoin?