The main historical data that we do get from Homer is linguistic. We learn a lot about phonological developments and the relationship between dialects, and a fair amount about changes in vocabulary over time. We learn that there was a poetic intersection between the Aeolic and Ionic dialects, though there’s active disagreement over the historical relationship between them in the poetic tradition. We learn from Homer that early Greek preserved a sound known as syllabic r (in effect, ‘r’ treated as a vowel) which otherwise survives only in some Indic and Slavic languages. We suspect that there’s a genetic relationship between a handful of Homeric phrases and poetic phrases found in other Indo-European traditions.