- Don't invest in bitcoin because friend lost money by invest in PONZI scheme that use bitcoin as their tool.
- Don't trade on crypto exchange as my friend lost his crypto on a scam exchange.
Choose good tumblers and you will have bigger prob to be fine rather than to be scammed. Give your friend two topics and ask him to check any tumbler in the future.
Ofcourse, there are also scam/clone ETH mixers: [Be Aware]: Fake Ethereum and USDT Mixers
Most people here though will be more versed on bitcoin mixers: 2021 List Bitcoin Mixers Bitcoin Tumblers Websites.
Some explorer tools can be use to connect ETH addresses and transactions, you should know it:
https://ethtective.com/
https://blockchain3d.info/how-to-use/: will support ETH soon.
(Compilation) What is the best Ethereum explorer