My old training plan for Unbound XL (which I did not too far from your weight—former strength athlete). I don’t think TR is good out of the box for ultra endurance and disagree with the Gran Fondo rec (sorry TR folks). But with some manual adjustments to the polarized plan you can get something effective.
The elevation grade doesn’t look too bad. Obviously don’t burn out your top end in the first half. Fwiw, I think the optimal climbing strategy changes for us heavies. Slow grinds out of saddle can be more energy efficient, in my experience, with some practice. For me, sustained double digit grades is when walking might be a better use of energy. I actually drill marching up 15% inclines on the treadmill ahead of certain races. But the profile doesn’t look crazy on what you’ve linked.
EDIT: I should note that training for ultras also differs depending on whether you’re still building much of the required endurance adaptations. My linked plan assumes the distance will be a new challenge. Building endurance adaptions requires long, consecutive hours in the saddle (which TR Gran Fondo is not going to give ya). In my experience (and that of all the other racers I know), the endurance adaptations stick around for a long time. You just get to the point where any distance seems finish-able, even when you’ve been off the bike for months and your top end is in the gutter. Some racers will ease up on the long rides outside of their races/events and mostly focus on raising the ceiling of their top end from week to week, +/- some strength training. Which is counter to some of the things said here in this thread.