Alpine Guide — ruling 1

If Alpine Guide can't attack for any reason (such as being tapped or having come under a player's control that turn), then it doesn't attack. If there's a cost associated with having it attack, its controller isn't forced to pay that cost, so it doesn't have to attack in that case either.

Alpine Guide : règles, fonctionnement et interactions (MTG)

Alpine Guide is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

When this creature enters, you may search your library for a Mountain card, put that card onto the battlefield tapped, then shuffle. This creature attacks each combat if able. When this creature leaves the battlefield, sacrifice a Mountain.

How it works : Alpine Guide

Original English text — Wizards of the Coast / Scryfall

#1June 14, 2019· Wizards of the Coast
If Alpine Guide can't attack for any reason (such as being tapped or having come under a player's control that turn), then it doesn't attack. If there's a cost associated with having it attack, its controller isn't forced to pay that cost, so it doesn't have to attack in that case either.
No other card is named in this ruling.