Tell them to buy a Ledger hardware wallet. It's not that difficult. My grandma probably wouldn't know how to use it, but if they're tech-savvy enough to trade crypto on those exchanges they'll be fine. It comes with a nice app/UI as well.

However, if your friends are not tech-savvy be sure to educate them about storing their keys in a safe way. Writing their recovery phrase onto a post-it note and storing it on Google Drive is more dangerous than leaving their money on exchange like Coinbase. Of course the hardware wallet come with instructions, but who reads instructions these days?

After a small amount of Googling I've found that a "self-custody" wallet app could provide enough user friendliness. What are some good wallets that allow exporting the private key? e.g. The Coinbase wallet app provides a recovery phrase to recover the private keys through the app, but what happens when the Coinbase app stops working? Ideally a wallet should provide an option to export the raw key (with all of the consequences of course ...)

You might need multiple self-custody’s wallets depending on what tokens you’re holding.

The Coinbase recovery phrase you mention is a seed phrase that you can enter in any ETH compatible wallet, the seed phrase lets you easily recover all the wallets generated by the phrase. A private key will only recover the singular wallet that it’s connected to.

Good to know, is this based on some standard i.e. can I generate the key-pairs myself based on the seed phrase?

Didn't catch your reply.

With the Ethers.js library it is trivial [1] to generate key-pairs from a mnemonic phrase. You might be interested in vanity address generator [2].

The Brave Wallet GitHub Wiki [3] has a write up with good links for further research.

[1] https://docs.ethers.io/v5/api/signer/#Wallet.fromMnemonic

[2] https://github.com/bokub/vanity-eth

[3] https://github.com/brave/brave-browser/wiki/Brave-Wallet-See...

The Maiar mobile application is a non-custodial wallet, with a nice UI/UX and easy onboarding. You are in full control over your keys, and they are not synchronized with the server. It even offers a secure cryptographic method to back up your keys. https://maiar.com/

When bitcoin was being evangelised in its early days, a person who was vehemently promoting the digital currency was once asked during his presentation this very question. His reply? He said, he himself prints all the keys on a paper and keeps it in safe custody. This was in addition to other digital mechanisms.

I'm a bit confused by this - sounds great in principle, but aren't keys effectively one-time use, and need to be continuously regenerated, or... something bad related to privacy happens?

This is still a thing, see bitcoinpaperwallet.com

As a crypto-bro I'm not sure what you said. Crypto are funds.