This is a curious question, as it can be taken a few ways. Do they mean adapting the rules to a different setting, or adapting the setting to fit a rules set?

Let’s start with the first option. I have, over the course of 30 years, used James Bond: 007 RPG from Victory Games for a number of different settings. I’ve run Cyberpunk using the rules, which required the creation of cybernetics rules. I’ve used it for Stargate, which required creating ways to render aliens in the mechanics. It’s a versatile set of rule that can be poked and prodded, but which start to fall apart as scale gets above, say, a coast guard cutter, for spaceships or vehicle combat.

A setting that begs for better mechanics is Space: 1889. The original GDW rules were bolted onto their Sky Galleons of Mars boardgame, more or less. I ran this setting using the GDW game, then using a home-modified version of Castle Falkenstein until about 2006. The new release of the setting by Clockwerk in Germany and Modiphius in the UK, uses the same Ubiquity system as Hollow Earth Expedition, and works well.