If internal link building is something you do, then how challenging is it?

Not very challenging. Maybe just a little at the beginning when you don't have enough consents.

Internal link building can indeed be a challenging task, requiring a strategic approach to ensure relevance and value. However, when executed correctly, it significantly enhances site navigation and boosts SEO performance.

Fortunately, this is much easier and quicker than building external links.

Internal link building can indeed be a challenging task, especially when trying to maintain a balance between user experience and SEO optimization. However, with a strategic approach and the right tools, it becomes a manageable and highly beneficial process.

It is very little challenging. You just read the whole site and link where it is reasonable to link.