I love my Fizik Arctica winter SPD-R boots in dry conditions and ride them at temperatures up to 60ish degrees. They are not the last word in warmth when temps go down in the 30's but so long as its dry my toes don't freeze too badly. It's when it rains that these "winter boots" are mystifyingly inadequate - for example, it might just be a light drizzle or some residual water on the road, but by some stupid lack of waterproofing, the internals get super wet and often the interior of the boot will be completely waterlogged in no time.
I have a can of the black paint on waterproofing - the stuff they advertise on TV where the guy cuts a boat in half and sticks the waterproof tape on it (what's that stuff called?) - anyway, I plan to just pull the insoles on the Arctica boots then use a paint brush on the insides of the shoes. I really can't see any major holes in the bottom of the Artica boots, perhaps the water is coming in through the SPD screw holes, I really would like to know.

I did purchase some Lake winter boots in the same size (46.5 euro) and they look more the part like they would be warmer, not sure if they have superior waterproofing or not.
Just curious to know if you have read this far if you have any waterproofing tricks I could deploy that might keep the interior of my boots dry during cold wet weather riding stints - thanks a lot!

The Fziik website says the Terra Artica boots are GoreTex waterproof. You’re saying that’s not the case. Complain to Fziik ?, maybe they’ll send you new shoes.

Which Artica are they? I have the old model with laces and they are indeed waterproof, provided you don't let water drip down your legs into them. I wear Castelli water resistant tights that I added stirrups to in order to keep the cuffs below the shoe opening, and get no water ingress.