Learn Russian: Благодаря смартфону у нас есть доступ к информации. - Thanks to the smartphone, we have access to information.

The preposition благодаря (thanks to) always requires the Dative case. Since смартфон is a masculine noun ending in a consonant, it takes the -у ending in the Dative case.

Could I use из-за instead of благодаря here?

You shouldn't. While both can translate to 'because of', благодаря is specifically used for positive causes ('thanks to'). Из-за is used for negative causes ('due to [something bad]'). Also, remember that из-за requires the Genitive case, while благодаря takes the Dative.

Why do we use the preposition к before информации?

In Russian, the noun доступ (access) pairs with the preposition к (to/toward) to show what you have access to. Just like благодаря, the preposition к also requires the following noun to be in the Dative case.

If к takes the Dative case, why doesn't информации end in -е like most feminine nouns?

Информация is a feminine noun that ends in -ия in its dictionary form. Nouns ending in -ия follow a special rule: in the Dative (and Prepositional) case, they end in -ии instead of the standard -е.