Additionally, the mkimage command in the SDK relies on `libssl1.1`. Sometimes the system won't contain that because it has been deprecated, use `dpkg -s libssl1.1` to check if you have installed it.
If not, the following two methods are both applicable:
1. Installation with additional repositories
```bash
echo"deb http://security.ubuntu.com/ubuntu focal-security main" | sudo tee /etc/apt/sources.list.d/focal-security.list
sudo apt update
sudo apt install libssl1.1
```
2. Manual download and installation of the deb package