heimdall still works, especialy for old devices like the j6primelte, when it is simple to just flash recovery.img, it is simply complicated to use to install full Samsung firmware (you have to be precise and exhaustive)
https://forum.xda-developers.com/t/guide-flashing-with-heimdall.878686/
[HOWTO] (Needs expert review) Flash Galaxy s9+ to Stock Android 10 using heimdall-gui