It is my understanding that a planet orbiting a black hole receives only light, and no heat...
This assumption is only for a non-feeding, non-rotating black hole. Stellar black holes (ie. they formed from a collapsing star) always rotate and, if there's a planetary system still around them after the collapse of the star, are often feeding.
Tidal Heating
Our hypothetical planet can get as close to the black hole as we like, so long as it stays outside the Roche Limit where it will be torn apart. As it orbits, it experiences tidal forces which tug on one side more than the other. The planet is literally stretched out. As it rotates, the direction the planet is stretched changes. This constant flexing produces tidal heating which provides heat to the planet. Europa, orbiting Jupiter, is such an example.
This would power your geothermal pockets.
Feeding
This is the simplest way to get energy out of a black hole, throw stuff into it. Thus the term "feeding".
As the matter stream spirals towards the black hole it forms an accretion disk around the black hole. Friction causes it to heat up and emit electromagnetic radiation: light. If the mass of the black hole is just right, the accretion disk can emit visible light.
Trouble is the black hole needs something to feed from. Usually this is another massive star, but there's no such star in your system. Nothing else is massive enough to provide energy on the time scales necessary to evolve life.
Hawking Radiation?
While black holes do emit radiation from Hawking Radiation, and it can be quite a bit, it doesn't emit enough of it consistently enough and for long enough for life to evolve.
The problem is the smaller the black hole the more Hawking Radiation it emits. Large black holes last a very long time, but emit very little radiation. Small black holes emit a lot more energy, but don't last long. By the time it's emitting enough energy to warm a planet it's smaller than the planet and won't last very long.
A 3 stellar mass black hole, the minimum needed to form a stellar black hole, would radiate 1e-29 W of power and last 6e68 years. This is an infinitesimal amount of power over an unfathomable period of time.
A 1e10 kg black hole emits 3.5 TW of power, but will only last 2.7 million years. That's a lot of power, but isn't enough to warm a planet. And 2.7 million years is a long time, but not in geological terms; it isn't long enough for life to form.
This is less massive than even a dwarf planet like Ceres by 10 orders of magnitude, so the black hole would be orbiting the planet (a pretty cool idea!)
Up the power to usable stellar levels and the lifespan gets shorter.
A black hole that emits as much energy as a dwarf star via Hawking Radiation is just 1e5 kg and will last 80 milliseconds.
Such a small black hole could not have formed naturally, it could only have come from a stellar mass black hole that's had 1e68 years to evaporate. So either your setting is in the Black Hole Era (which would be cool) or this tiny black hole is artificial.
How Did It Survive The Death Of A Star?
How did this planet wind up around a black hole? Typically black holes form from a massive collapsing star. Presumably this planet formed with the star and somehow survived the star's usually very energetic death without having all its lighter elements (ie. what makes up organic life) burned off.
If it was instead captured by the black hole it would have a very eccentric orbit taking it periodically very close to and then far away from the black hole producing an unstable climate unsuitable for sustaining life.
What Would A "Jungle" Look Like?
Not like the Rogue Planet on Enterprise where they can freely walk around in a warm Earth-like jungle. There's numerous problems with that.
There would be no atmosphere, even near the vents. Most of the planet would be too cold and the atmosphere would have long since frozen. The vents would heat the surface and produce gases, but it would quickly dissipate into the surrounding near-vacuum and freeze again. Without an atmosphere to conduct heat the vents would warm only a very, very small radius.
Another is the lack of light (visible or otherwise) for photosynthesis. You might instead have life forms optimized with high surface areas to absorb as much heat as possible from the vents, but without an atmosphere they couldn't get very far nor very complex.
More likely the planet would be like Europa with a thick sheet of surface (not necessarily water) ice. This would provide insulation for a core kept active by tidal heating. Below would be a liquid (again, not necessarily water) layer which could support life. The liquid layer would conduct heat and provide a stable environment for life to evolve.
There would be no "plants" because there's no light for photosynthesis. Instead it would look something more life around a deep sea hydro-thermal vent on Earth. Rather than photosynthetic organisms being at the bottom of the food chain, chemosynthetic organisms would be at the bottom of the food chain turning the chemicals and heat coming from the vents into energy.
You could get something akin to plants from organisms adapted to collect as much heat and chemicals as possible, such as giant tube worms. They would either be working in a symbiotic relationship with chemosynthetic organisms, as tube worms do, or have fully integrated them into their biology, like chloroplasts in plants.
