In 1991, Origin Systems gave Game Boy owners a taste of the Ultima series with a unique entry, Ultima: Runes of Virtue. Unlike many Ultima spinoffs, this was actually developed in-house at Origin Systems, by many longtime Origin staff who had most recently worked on Ultima VI: The False Prophet. As a result, the art style in this games resembles Ultima VI.
Instead of a turn-based RPG, Origin opted to develop this game as an action-adventure game in the vein of Zelda. It was a Game Boy Zelda game a couple of years before Link's Awakening, and a contemporary of Square's Final Fantasy Adventure.
In this game, the Black Knight has stolen the eight Runes of Virtue. You select one of four heroes - Dupre the Paladin, Shamino the Ranger, Mariah the Mage, and Iolo the Bard, who appear in the mainline Ultima games as the companions of the Avatar - and head off on a search for them.
I've never gotten into Ultima, but I think that's interesting they made a Game Boy game and it's reworked to be an action adventure game.
After I played Secret of Mana on the SNES, I went back and played Final Fantasy Adventure on GB because even back then, I knew those games were related. It was good, but still couldn't hold a candle to Link's Awakening. But then, Link's Awakening is my number one favorite Zelda game. In fact, I was more excited when Nintendo announced the Link's Awakening remake on Switch than I was about the Ocarina of Time remake they just announced at the last recent Direct.
I've been curious about this and have been trying to find it locally with no luck. Interesting. I was kind of hoping for turn-based though.