[Samsung Galaxy A7 (2018) Guides, News, & Discussio] Jotaro_Kun:
I AM NOT RESPONSIBLE FOR ANY MISHAPS OR YOU BEING CLUMSY BEFORE DOING ANYTHING I HIGHLY ADVISE YOU TO BACKUP THE NECESSARY DATA STORED ON YOUR PHONE

Before we proceed we must first unlock the phone's bootloader or otherwise you'll encounter "Only official binaries are allowed to be flashed" that being said let's go!

Unlocking Bootloader​

Unlocking the bootloader on modern Samsung devices have some caveats. The newly introduced VaultKeeper service will make the bootloader reject any unofficial partitions in some cirumstances.

Allow bootloader unlocking in Developer options → OEM unlocking

Reboot to download mode: power off your device and press the download mode key combo for your device

Long press volume up to unlock the bootloader. This will wipe your data and automatically reboot.

Go through the initial setup. Skip through all the steps since data will be wiped again in later steps. Connect the device to Internet during the setup.

Enable developer options, and confirm that the OEM unlocking option exists and is grayed out. This means the VaultKeeper service has unleashed the bootloader.

Your bootloader now accepts unofficial images in download mode

PBRP installation

First and foremost PBRP doesn't seem to work properly on the latest build of the OS so we might have to downgrade on an older build of the OS which is from 20200817105004 with a security patch level of 2020-08-01 otherwise we'll encounter issues that users have experienced on the latest build of the OS, so let's get started

Use either samfirm.js, Frija, samfw or Samloader to download the older build firmware zip of your device directly from Samsung servers.

Reboot to download mode. Open Odin on your PC, and flash AP, together with BL, CP, and CSC.

Your device should reboot automatically once Odin finished flashing.

Go through the initial setup. Skip through all the steps since data will be wiped again in later steps. Connect the device to Internet during the setup.

Enable developer options, and confirm that the OEM unlocking option exists and is grayed out.

Download this file.

Reboot to download mode. Open Odin on your PC and flash the downloaded file.

Reboot to recovery and voila! You now have PBRP.

Root installation

Use the firmware zip you installed earlier.

Unzip the firmware and copy the AP tar file to your device. It is normally named as AP_[device_model_sw_ver].tar.md5

Rename AP_[device_model_sw_ver].tar.md5 to AP_[device_model_sw_ver].tar

Open and extract boot.img.lz4 which it will leave you boot.img

Copy the extracted boot.img file to your phone.

Press the Install button in the Magisk card.

Choose “Select and Patch a File” in method, and select boot.img

The Magisk app will patch the file to [Internal Storage]/Download/magisk_patched_[random_strings].img

Copy the patched boot.img file to your PC.

Rename the magisk_patched_[random_strings].img to boot.img and repack it as tar file format.

Reboot to download mode. Open Odin on your PC, and flash boot.img.tar as AP.

Your device should reboot automatically once Odin finished flashing.

Install the latest Magisk app and launch the app. It should show a dialog asking for additional setup. Let it do its job and the app will automatically reboot your device.

Voila! Enjoy Magisk

Credits

@topjohnwu - For magisk

@itmr - For compiling and making PBRP.