Adobe says Lightroom needs a GPU with a minimum of 2GB VRAM and a benchmark score of 2000, which is pretty low. So even relatively old GPUs work. Puget Systems, who build computers for photo processing found:
"What GPU (video card) is best for Lightroom Classic?
Lightroom Classic does not really utilize a modern video card for the majority of tasks, so we generally recommend a mid-range GPU to handle the needs of other related applications like Photoshop that do use the GPU more heavily."
and also in their testing:
"Overall, we didn't see much of a difference between the various GPUs we tested, or even the test using just Intel integrated graphics and GPU acceleration disabled entirely. NVIDIA is definitely a hair faster than AMD (which oddly was slower than having no GPU acceleration at all), but the performance between each NVIDIA GPU is close enough to be within the margin of error. In fact, Lightroom Classic tends to have a larger margin of error than our other benchmarks, and anything within ~5% we would consider to be effectively the same.
We could go into our results in more detail, but what we are taking from this is that for what we are testing, the GPU has almost no impact. As we mentioned earlier in this post, we do hope to include a number of other tests that should be a better indicator of GPU performance, but this simply reinforces that your GPU is a low priority relative to your CPU, RAM, and storage."
