I’ve never actually run any of the old modules like Keep on the Borderlands or anything like that. I’m much more used to homebrewing a setting entirely or at most grabbing a few elements from a published adventure (I took a bunch from Willow, for example). I think this is why most of my favorite systems tend to be more in the NSR camp; I just never end up needing compatibility with older material.
Is running retro adventures in their entirety the most common practice for OSR tables? Or is the homebrew approach how most people are doing it?
In my experience, it seems like (from what I’ve seen on the web, so there’s possibly a bit of sampling bias there) that homebrew is somewhat more common, but it’s definitely a mix. Personally, my way of doing things is to take old modules and take bits and pieces from them as inspiration.