Solar panel installation on a old vintage roof
Well it depends, many old roofs of this age had 1x boards nailed to the rafters some were later overlaid with plywood But in either case I would feel better about mounting solar on a old roof than one with OSB especially if a coastal area or desert where you get high winds regularly through the year.
There are those that only look at the size of the rafters and think because they only used 2x6 and today we use 2x8 that the roof needs to be built up, this is not true the old lumber prior to the 60’s had ring counts required (ring counts were taken out of grade books in the late 60 early 70’s) what is the difference.
In your old structures especially Victorians the lumber used had 3-5x the rings and was clear no nots or possibly small ones and no wane or bark today it takes a larger rafter to hold the same load.  So your roof would be a better candidate in my opinion. Will it hurt the wood to anchor the panels, if the lags are pre drilled and not oversized then properly sealed even your old roof will be fine.
That old tight grain has more holding power than what we call lumber today, I currently work in a mill and have photos of #2 4x4 with a swirl 5 branches in other words a Christmas tree made into lumber when they used to use 150+ year old trees. I believe your roof will be fine.