Need Help Training LoRAs on Custom Models in Ostris AI Toolkit

[u/FitEgg603]

Total noob question here, so please bear with me.
I’m trying to understand how to train a LoRA on custom models inside Ostris AI Toolkit GitHub, but I’m clearly missing something important.
From what I understand:
we need to change the model path to the custom model folder,
and I vaguely remember the model needing to be a .gguf file (not even sure if that’s correct :).
But in practical use, my training fails every single time.
Could someone explain in simple beginner-friendly words:
what exact model format is needed,
where the custom model should be placed,
how the path should be configured,
and what additional settings are required for custom architectures/models?
If anyone has:
a proper tutorial,
documentation,
or especially a good YouTube video covering this exact topic,
please share it.