I'm in the US and I have successfully sold my used gear on Mercari. As a woman, I don't want to be meeting up with strangers, and Mercari provides a safe platform to interact with buyers. I sold my 24-70GM just a few weeks ago. I got about 60% of new retail price, but 2x what KEH offered. They do take their fees, but to me it's worth the protection and ensuring that I get paid.
One note though is that all transactions over $600 will be reported to the IRS and it helps to have the original purchase receipt to offset the income taxes.