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There seems to be enough gap under the front fender to permit the 110/90 to fit - and I have heard of people running that size (but can't remember what brand).
There isn't much clearance with the standard tyre (little more than 15 mm) and that could be a problem, as different manufacturers / different categories may be slightly taller than the "nominal" 110/90 that you mentioned. A tall-ish 110/90 might not actually touch the fender [when stationary], but might grow a shade taller with the centrifugal force at high speed of revolution.
The other problem with minimal tyre-fender clearance is that your wheel could seize up after gaining only a small coating of mud [on wheel and/or inside of fender]. You may have the best of intentions that you will never be going off the bitumen - but sometimes these unintended events come to pass, even if just a few dozen yards of muddy access road. And your first warning of the mud build-up, will be your front wheel skidding out from under you. Uncontrollably !
A similar problem can happen when a piece of gravel gets flung up under the fender (or carried up, stuck in a groove in the tread).
These sorts of problems can still happen with the standard-size 110/80, but at least there you have a much larger safety margin.
* The 110/80 R 19 should, by rights, be using the "R" as referring to Radial Construction (rather than the R speed-rating of 170 kph / 106 mph).
Close by that size information will be the load & speed rating - expressed as something like "59V" or "60H" or "62T" or somesuch alpha-numerics.
A 110/90 tyre, being bigger in height & volume, will hold more air and therefore carry a higher max load than a comparable 110/80. So it may well show a higher load rating than "59". But higher than the (stock) "59" is of no real benefit for a front tyre.
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