I conducted a search on your topic and the countries that came out of my search was;
. Singapore
. Switzerland
. Netherlands
. El Salvador
. Vanuatu
As an avid crypto trader/investor, the above listed country are the crypto-friendly countries that could be perfect for you as they embrace the inherent volatility of cryptocurrencies. Those five countries have a good reputation being the most crypto-friendly country.
More information is contained here:
https://learn.bybit.com/investing/most-crypto-friendly-countries/Based from the list, I only know El Salvador having bitcoin as legal tender. As the OP is asking which countries are having btc as legal tender also. Others may have loose regulations when it comes to crypto but the OP should look into these countries closely if he is planning to visit in one of them. They have their own protocols when it comes to crypto and you also don't know how wide is the coverage of the crypto usage among its merchants.
The current era has seen the highest development among cryptocurrencies. The whole world knows about it. Considering its payment convenience and cost aspect, many have chosen it as their preferred payment method. I would like to mention here the names of some countries that are user friendly with the use of crypto. They are El Salvador, Portugal, Germany, Luxembourg, Estonia, Singapore, Malta, Canada.