How do I recover access to my locked MacBook?

• Did you use this method to change your Apple Account to the new email address:

Change your Apple Account primary email address - Apple Support

• Did you ever attempt to delete/deactivate your old email using this method?

Understand and control the personal information that you store with Apple - Apple Support

• What is the issue you experienced getting into contact with Apple? Is support not available in your region?

Contact Apple Support - Apple Support

• Removing the Activation Lock is done by submitting the required documentation and following the link here:

https://al-support.apple.com/#/additional-support

If the Mac is signed into your new email account, you can sign in online here and that device will be listed where you can remove the Mac from your account. Those are the devices that are linked to your Apple Account. This will get rid of the Activation Lock, although you may have to restart your Mac after it has been removed. And since, you have an Intel Mac, I would also recommend resetting the NVRAM, just in case there is a glitch with your old email still being cached.

• Remove a device from Find Devices on iCloud.com - Apple Support
• Reset NVRAM on your Mac - Apple Support

This sentence is unclear to me:

I would still say it is bug in system as it is not logical for it to ask my old email address as I changed it (it was my primary email before, but as I mentioned email provider was shut down ..). And also in apple finder, my Macbook was visible .. so it was linked to this account.

Your email provider shutting down has no effect on your Mac or ability to sign in. It just requires that email/password and will continue to work whether that email account is still valid or not. Did you use the method to change your primary email account from the link I posted earlier or was it changed some other way? In Finder, your MacBook would still be visible no matter what account was signed into the device, in fact it would still be visible even if there was no account linked to your Mac. Also did you Delete/Deactivate the previous email address with the provided link that would make it no longer valid?

You are correct that support is limited in your region and Activation Lock removal through Apple is not possible without the original purchase receipt from Apple or Authorized Apple Seller. Sorry, I cannot be more helpful other than the information I have provided. Since the Mac is an Intel Mac and I don't believe it has a T2 chip, it may still be possible to erase it and use it again, although of course that means your data is lost.

1. Start up from macOS Recovery.
2. Use Disk Utility to erase your Mac from Recovery.
3. Reinstall macOS from Recovery.