Specific to newer Samsung and LG devices, there are full guides from RootJunky on YouTube. Your user can probably start at step 4.
Reboot into Recovery mode (hold Home, Volume Up, and Power, releasing Power when you see the device turn on/reboot).
Perform a Factory Reset (press Volume Down until wipe data/factory reset is selected, press Power, scroll down to Yes -- delete all user data and press Power again).
Proceed through the device Setup Wizard until it prompts you for the Google account credentials.
For a Samsung device, save this RootJunky APK onto a USB flash drive, and connect it to the device via OTG.
For LG:
Back up, connect to Wi-Fi, then back up again and hit Accessibility (Yes to the prompt that follows).
Turn "Switch Access" on, then enter its Settings and set a key for Overview, such as Volume Down.
Back out to Accessibility again, go to Vision → Talkback → Settings → Privacy Policy to open the browser, and download the APK linked above (rootjunkysdl.com → Apps).
Press the key you set up for Overview, hit Dual Window, and select the file browser.
When the File Explorer launches, browse to and tap the APK to install it. When you get the prompt about unknown sources, choose the Settings option and enable the Unknown Sources option.
Complete the install and choose to Open the application, which will open Settings.
For LG:
Add a new user account under Users, switch to it and add your own Google account via Setup, then switch back to the main user (Owner) from Settings → Users, and back out from there to the main Settings.
Go to Backup and Reset and do a Factory Data Reset. As per my other answer, this will remove FRP from the device.
The APK in (4) is very simple and just opens Settings, you could use any other that does the same if you don't want to trust that source.
For other devices, or after this exploit is fixed, see my other answer.