When I built my gravel bike out of a 90s MTB I changed it from 3x7 to 1x10 (34x11-36) and put it on 700c wheels. In truth I did it because I could, because it was a thing, because why not? It turned out well enough though - I geared it to ensure I could climb and it does spin-out quickly on road descents but then I am not riding it as a fast road bike so I am happy to freewheel. I love the simplicity and cleanliness of no front mech and a single chainring and I have not noticed the bigger jumps between gears compared to a multi-ring bike; or at least I have not noticed a time where I couldn't find a gear that fitted the situation.
My 27.5er full-sus is 1x12 (34x10-50) - as noted up-thread it's a pricey cassette to replace, when the time comes, but again for the places I take it it has all the gears I need and a nice clean appearance and setup. My 29er hardtail is 3x10 (42-32-24x11-36) which, in truth, is more gears than I need - I do 90% of my time on the middle ring, 9% on the granny ring winching up hard climbs and 1% on the big ring on the rare fast downhill; I am considering changing it to a 2x up front. This bike has demonstrated the challenge of a FD though as in proper claggy mud the FD can get clogged up, occasionally enough to need a stop to clear it.
I too have a gearing spreadsheet that I used a lot when deciding on my gravel build and am using to consider the 2x modification and also whether to change the gravel setup for a wider cassette and bigger ring.