If you're using MultiMC or a fork,
Go edit > settings > Java arguments (click the check box)
put this in there:

-Dminecraft.api.auth.host=https://nope.invalid -Dminecraft.api.account.host=https://nope.invalid -Dminecraft.api.session.host=https://nope.invalid -Dminecraft.api.services.host=https://nope.invalid 

This allows you to bypass the arbitrary Microcock account restriction and play on
cracked servers accordingly.