The very fastest way would be to use a service until you dig further into the details and withdraw occasionally to a non-custodial wallet.

Example setup that will work in minutes:

• I'm a huge fan of the Alby browser extension. Download and create an account. You will receive what looks like an email address underneath the "accounts" section that ends with "...@getalby.com"

• Copy/Paste that address onto a website or in a tip jar window for whatever you are hoping to receive donations for.

• Then download the Phoenix wallet on your mobile phone (its a non-custodial lightning wallet)

• Backup your seed/wallet on Phoenix, then when you have $20 or so worth of tips in your Alby after a few people send you some sats, send it to your Phoenix wallet.

• Rinse and repeat

When your Phoenix wallet has a lot of sats, a meaningful amount, then send it to your cold storage simply by putting in a BTC address and it will automatically do a swap for you.