What do I need to do to regain access to my icloud? I've switched phones and no longer have an iPhone.

See about: How to use account recovery when you can’t reset your Apple ID password - Apple Support

(I have not memorized all of Apple's URLs so I don't know where untitled links others have posted earlier take you and it's easier for me to just post mine even if it duplicates what others have said.)

- "If you use two-factor authentication and can’t sign in or reset your password, you can regain access after an account recovery waiting period."

However, note you will ultimately need some kind of information demonstrating you know enough about the account to convince Apple to help you:

Security and your Apple ID - https://support.apple.com/HT201303

"Without proof of your identity ... and other carefully selected criteria(1), Apple Support can't help you perform any actions on your account."

Hi,

If your Apple ID has been locked or disabled due to security reasons, it is due to the incorrect password being entered too many times or the current password no longer meeting the password requirements.

Typically, when you try to sign in to the Apple ID website, you’ll receive a pop up to unlock your account, tap unlock, and then enter a new password.

If this does not apply to you, you will need to set up account recovery. That is the only way you will be able to regain access to the Apple ID.

To start the recovery process, you will go to iforgot.apple.com, enter your Apple ID email, and then confirm the trusted phone number associated to the Apple ID. You do not need to still have access to the number. You only need to confirm it.

Once confirming the number, it will attempt to send a verification code to that number.

Select the option Can’t use this number/Don’t have access to this number and you will then be prompted to enter a new phone number, followed by a verification code sent to that number.

You can complete the recovery process from here.

https://support.apple.com/en-us/HT204921

If you cannot confirm the trusted phone number, you cannot set up account recovery, and you will not be able to regain access to the Apple ID.

It's unlikely you'll be able to regain access as you have nothing with which you could prove ownership of the account. Feel free to use the "get support" link above to contact support.

You'd have to contact support and see what they say. Even if you are able to start an account recovery, those can take a very long time.

If your account was disabled: https://support.apple.com/en-gb/HT204106