Prior work on Knowledge Graph-to-Text generation has mostly evaluated models on in-domain test sets and/or with English as the target language. In contrast, we focus on Russian and we assess how various generation methods perform on out-of-domain, unseen data. Previous studies have shown that enriching the input with target-language verbalisations of entities and properties substantially improves the performance of fine-tuned models for Russian. We compare multiple variants of two contemporary paradigms — LLM prompting and Retrieval-Augmented Generation (RAG) — and investigate alternative ways to integrate such external knowledge into the generation process. Using automatic metrics and human evaluation, we find that on unseen data the fine-tuned model consistently underperforms, revealing limited generalisation capacity; that while it outperforms RAG by a small margin on most datasets, prompting generates less fluent text; and conversely, that RAG generates text that is less faithful to the input. Overall, both LLM prompting and RAG outperform Fine-Tuning across all unseen testsets. The code for this paper is available at https://github.com/Javanochka/KG-to-text-fine-tuning-prompting-rag