I suffered the CIA-hack and now can't use recovery

by invoking the boot screen by pressing ALT at startup.

I hit enter when the external MicroSD is visible and selected and immediately after that CMD-R.

Why, what happens if you just select the drive you wn't boot from instead of CMD+R?

 Start up from macOS Recovery

Option-⌘-R

Upgrade to the latest macOS compatible with your Mac.

APFS won't work for Sierra, Sierra needs MacOS Extended Journaled. High Sierra won't work for APFS on earlier Macs.

What has often worked for others is to use this Restore Method instead of CMD+r keys...

Option-⌘-R

Upgrade to the latest macOS compatible with your Mac.

https://discussions.apple.com/thread/254793247?answerId=258936149022#258936149022

Clean Install of High Sierra: Multiple Fa… - Apple Community

An Error Occurred While Preparing The Ins… - Apple Community

Thanks to Clo3y…

https://apple.stackexchange.com/questions/309399/how-can-i-download-an-older-version-of-os-x-macos

A1. Start up from macOS Recovery

To start up from macOS Recovery, turn on your Mac and immediately press and hold one of the following combinations on your keyboard. Command-R is generally recommended, especially if you never installed macOS Sierra 10.12.4 or later… How to reinstall macOS - Apple Support

Command (⌘)-R

Install the latest macOS that was installed on your Mac.

Option-⌘-R

Upgrade to the latest macOS compatible with your Mac.

Shift-Option-⌘-R

Install the macOS that came with your Mac, or the closest version still available.

2. Decide whether to erase (format) your disk

If you need to erase your disk before installing macOS, select Disk Utility from the Utilities window, then click Continue. You probably don't need to erase, unless you're selling or giving away your Mac or have an issue that requires you to erase. Learn more about when and how to erase.

3. Install macOS

After starting up from macOS Recovery, follow these steps to install macOS:

1. Choose Reinstall macOS (or Reinstall OS X) from the Utilities window.
2. Click Continue, then follow the onscreen instructions to choose your disk and begin installation.
3. If the installer asks to unlock your disk, enter the password you use to log in to your Mac. If it doesn't see your disk, or it says that it can't install on your computer or volume, you might need to erase your disk. 

1. Please allow installation to complete without putting your Mac to sleep or closing its lid. During installation, your Mac might restart and show a progress bar several times, and the screen might be empty for minutes at a time.

If your Mac restarts to a setup assistant, but you're selling or giving it away, press Command-Q to quit the assistant without completing setup. Then click Shut Down. When the new owner starts up the Mac, they can use their own information to complete setup.

If you never installed macOS Sierra 10.12.4

If macOS Sierra 10.12.4 or later was never installed on your Mac, macOS Recovery works differently:

• Command-R is still the recommended way to start up from macOS Recovery. This combination makes sure that the installation isn't associated with your Apple ID, which is important if you're selling or giving away your Mac.
• Option-Command-R installs the macOS that came with your Mac, or the closest version still available.
• Shift-Option-Command-R isn't available.

How to reinstall macOS - Apple Support 

Of course you may need to make a USB installer...

Create a bootable installer for macOS - Apple Support...

Create a bootable installer for macOS - Apple Support

First off, did you verify the age and model number of your Mac?

http://checkcoverage.apple.com/

will tell us which recovery options are available to your machine. Please do NOT put your serial number here, as that's your own private information. We just need to know the year, and release of your Mac model as reported in verifying your serial number (which is found on the bottom of your computer).

Next, Intro to macOS Recovery - Apple Support

will explain how to use Recovery. Only use Recovery if your data is backed up, and you either have the space for a new partition, or plan to wipe the computer, or plan to make sure missing pieces of the current OS are installed.

And what evidence do you have there is a "CIA hack?"

You aren't talking to Apple here. You are talking to end users like yourself here with Apple moderation.

So when you make statements like "you just go and take care of that nose bleed of yours" I don't know who you intend to be speaking to.

The CIA is unlikely to be invading your space. For one thing, if you are taking care of the security, you likely would want to be using Filevault, and Openfirmware passwords which nobody can hack.

Quite contrary to many popular's opinion, there isn't just one Kevin Mitnick in this world.

https://forebears.io/surnames/mitnick

There are incidents of Mitnick in England and ireland, where Kevin is very common first name.

The odds of your running into that name. when there are at least a thousand in the U.S. and a scattering in U.K. and Ireland are not that rare.

Recovery might be blocked because the hard drive is close to failure, or a not to solid WiFi connection is selected. And there has been a rash of incidents of older operating systems on internet recovery not working very well. There may be something wrong with those servers on some of the older operating systems.

The best advice I can offer is to make clone backups of your system, and restore where when the server gets back up and running. Never depend on someone else's connection to offer a solution for you. If you want the help of us end users, please answer our questions, like how old your system is, and which model it is. We can then tell you the best likely recovery options you might have.