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Tundra_Man I got a Mudhugger for the rear and a Mucky Nutz Full Face for the fork. I got 29er versions for my plus bike. They have fat bike versions too. They keep the spray off the body but they don't direct everything to the ground like road bike fenders. Cuffs, boots, and drivetrain are still vulnerable. Portland Design Works sells a huge downtube mudguard and it would be a lot better than the Amazon cheapie I got, it was clearly meant for little old 26ers.
https://ridepdw.com/collections/mountain-and-fat-biking
I only need them for a few muddy months and a few rainy days here, not sure if that's solution enough for you.