What do we think of beer instead of white wine?

Dont do it

The flavor combination with beer isn't so strange; it veers into michelada territory if that's your kind of thing.

It's only 1/2 cup of liquid for a four pound bird that's supposed to serve 3 people.

In ancient times beer was brewed with a bunch of herbs and spices. Bavaria's 16th century purity law was partly enacted because of this wide variety of ingredients. In other places brewers continued to add various flavorings to beer.

Substitution with a mild lager should result in something quite pleasant. Use caution with beers with stronger flavor profiles (like today's trendy triple IPAs).

You will have to use your best judgment based on your dinner table guests' palates.

I have my doubts about roasted chicken + beer + lemon, fennel and thyme. I wouldn't try it with all those other flavors, which just seem incompatible with any type of beer Lots of onions, garlic and bay leaves? Yes. Lemons and fennel + beer? No, thanks. ;o)

Why not?
I first thought by analogy (there are lots of beef with wine dishes, but a few with beer are wonderful).
Then checked the web for other chicken-with-beer recipes and found many.
So, if you like beer, I would go for it.
If you're uncertain, I would go for a lager or IPA (lighter beer to not overwhelm the chicken and seasonings).
But other recipes called for dark beer, so either is ok, but will give a different flavor profile.