CGT is payable on realised Bitcoin profits at 20% in the UK.

Most onramps and most offramps for BTC are KYC'd meaning while the tax authority don't care how you made gains, they will take 20% of them.

There is a movement that looks at non KYC Bitcoin options such as Bisq, CoinJoin (Jam) and Liquid as obfuscation methods for Bitcoin, but ultimately if you want to spend your BTC profits in a fiat world you have to pay tax.

The UK does have an exit tax, you currently have to pay 20% CGT on unrealised assets (i.e. Bitcoin gains etc...) this is going up to 39% on the 30th October budget, The only unknown is when this 39% will come in to effect. 

If I cant exit before this raise comes into effect, I will remain a UK tax payer, but be non-dom.