Ibn Fadlan didn’t speak Turkic, so he used a limited number of words in his notes.
Several words don’t make the language. However, one can use these words to determine to which language family they belong. Turkic loan-words in Fadland’s notes are similar to the words found in Chuvash language belonging to the Oghur branch of Turkic languages
I provided a decent account of historic and present day facts.
Ancestors Chuvashes and Kazan Tatars lived at the confluence of Kama and Volga rivers in forest zone surrounded by several Finno-Ugric speaking peoples: Merja, Mari, Muroma, Erzya, Moksha. Modern day Oghur speaking Chuvashes are culturally and genetically similar to Finno-Ugric Mari. Kazan Tatars are genetically similar to Mari and Chuvashes. Ancestors of Chuvashes and Kazan Tatars were Finno-Ugric speaking people until the arrival of Volga Bulgars. Ancestors of Kazan Tatars adopted Islam in 921. After Mongol invasion during Horde rule ancestors of Kazan Tatars switched to Kypchak language that was lingua franca in Horde at the time. It’s not new about people adopting Turkic languages as it happened in what’s today Uzbekistan, Turkmenistan, northern Iran , Azerbaijan, Anatolia, northern Caucasus, Crimea and other places.
Turkic Sabir tribe could settle in forests of middle Volga but this is only a speculation. One can speculate
picking any Turkic tribe roaming through the great steppes from Altai to
Carpathians saying any of them could migrate north settling in middle Volga from whom Chuvashes’ ancestors picked up the language. Why would
nomadic Sabir tribe settle in forests on middle Volga? Bulgars settled
the region, after they were pushed by Khazars. Volga Bulgars continued paying tributes to Khazars until Sviatoslav of Rus defeated Khazar Khaganate.
Chuvashes, whose ancestors were subject of Volga Bulgaria, speak Oghur language to this day.