How did timber buildings/structures fare before the advent of chemical timber treatment? Were there accepted and effective ways of treating wood that have been prevalent throughout history?

Generally poorly. Please note, I am answering this from the perspective of an civil engineer, rather than a historian. I look forward to some more in-depth answers.

Currently what we use most often in consumer facing treated wood products is Copper (II) arsenate, which gives "pressure" treated wood the greenish color at the ends, where the pressure has forced the material in, and then it has bled out again, leaving extra copper behind (basically become a patina of copper). This preserves wood primarily form the arsenic killing anything that attempts to grow (molds or wood fungus) or consume it (termites).

Prior to this, various petroleum products (notably creosote) was used for pressure treating wood. In the US this is most often seen in older railroad ties and telephone pole, or in wood containing piers, walls, or other coastal structures. However, the use of petroleum based treatment requires the use of surplus heavy oils, only available in the modern post-industrial era.

Prior to that, you are looking at various local technologies and methodologies. Most of these, that I am aware of were all related to ship building, instrument making, and some furniture making.

Mediterranean communities uses salt preservation, but I don't think was very common for houses. Its most famous use was at the Venetian Arsenal, where they would store ship building materials in the arsenal's central pools. This would allow them to sorb salt, keep from rotting, and be available for ship building during wars or other periods.

Pitch pine and other high tannin trees were used, as were various tropical hard woods. These had natural resistance to fungus. Pines typically from natural products they produce to keep from freezing, and tropical hard woods from various compounds which were specifically anti-fungal.

For constructed buildings, paint was the way to go. Lacquer was used for small objects or ritual places (Reddit had some interesting postings on laq bugs last week), but to my knowledge it was not used for buildings (the Mahabharata had the House of Laq as one of the stories that the protagonists go through. Spoiler: They light it on fire and everyone dies; like a reverse Trojan horse). Recently in the historic sense, paint was still lead containing, and I am pretty sure has been lead containing for a long time. Being toxic to most living things, lead like arsenic is anti-fungal.

Otherwise, wood is not a good long term building material is most places. It is fast, reusable, renewable, but except in certain dry conditions it has both a tendency to rot or burn. If you were building from wood, you were building for yourself and for your kids. But after that (grand kids) you depended on repairs and maintenance.

I look forward to some better answers with actual links and references.