Learn Swedish: Jag tycker om kollektivtrafiken.

In this sentence, tycker om is a phrasal verb that means "like". By itself, the verb tycker means "to think" or "to have an opinion". The word om acts as a verb particle here, which changes the verb's meaning entirely.

How would the V2 rule apply if I started this sentence with a conjunctive adverb like "dessutom" (furthermore)?

If you start the sentence with a conjunctive adverb, the verb tycker must remain in the second position to follow the V2 rule. The subject jag swaps places with the verb, resulting in: Dessutom tycker jag om kollektivtrafiken.

Why is "kollektivtrafiken" in the definite form (ending in -en) when the English translation just says "public transport"?

Swedish often uses the definite form for uncountable nouns that describe general concepts, systems, or institutions. While English leaves it indefinite as "public transport", Swedish naturally says kollektivtrafiken (literally "the public transport").

When speaking, where does the stress fall in the phrase "tycker om"?

Because tycker om is a phrasal verb, the spoken stress falls heavily on the particle om, not on the verb. Emphasizing om is important because it immediately signals to the listener that you mean "like" rather than "think".