TLDR: The weak spot is the entire top of the tank, and it's weak to drones, explosives, or anything bigger than an automatic rifle. Also the donors took much of the advanced armor off because they were afraid about those secrets falling into Russian hands.
"We have a supreme weapon, but we don't want to bring it out and use it, because our rivals might copy it."
Author recommends that Ukrainians stop camping behind the minefields and no-man's-land, and charge forward with their 50 MPH M1A1s that Churchill himself inspired, using "manaeiouvrability" to "run riot" behind enemy lines, a completely foreign concept to inferior Slavic strategy patterns.