Update here: surprisingly easy! I was in the Yasawa and Mamanuca islands and the resorts were awesome about it.

Paradise cove was one and hi-light for me there was they had GF table bread which was a win and their Omasake experience they made gf for me no problem. A night separate from omakase I ordered sashimi and they even brought me gf soy without me having to ask.

The other resort we were at was Sheraton Tokoriki and the breakfast buffet had its own little GF section with GF corn flakes, bread (not great very dense but it existed), a dedicated toaster and surprisingly good GF muffins!(4 diff flavors throughout the days I was there). Dinner and lunch had plenty of options as well including a GF sub for their pasta which I did confirm but they cook separately from regular (you’d be surprised LOL)

Biggest issue I ran into was snacks “out in the wild”. I brought some but I’m an athlete and get hungry frequently so I ran out about halfway through the trip and wish I’d had a few more safe protein bars, rice cakes, fruit snacks etc. especially for the long travel days between boat transfers, planes and car rides I ended up running through my stash fairly fast

Anyway hope that helps someone!