Lightroom Classic is so slow that it is unusable. Are there any solutions?

[Cvatik]

I'm using a 2019 15" Macbook Pro, maxed out with the latest version of Lightroom Classic to edit 42 megapixel RAW images from my Sony camera.

-Moving sliders is insanely slow.
-The local adjustment brush is super delayed and basically unusable.
-Simply browsing through my catalog goes very slow.

The same images, the same catalog, are INSTANT on my 2008 Macbook Pro with an older version of Lightroom. No slow sliders, no delayed brushes, it's just perfect.

I've done all the basic troubleshooting. I've tried using smart previews. I've increased the cache. I have a lot of hard drive space. I've done every "5 things you can do to speed up Lightroom" article suggestion and I am at my wit's end.

I read somewhere that this has something to do with Apple pushing their new "Metal" architecture, but I'm not sure how much truth there is in that.

The GPU acceleration patch last year was supposed to fix these issues. It didn't. I can't be the only one having these problems.

Does anybody have any kind of solution? Otherwise, from now on, I'll be editing my images on my 12 year old laptop using a very outdated version of Lightroom.

[GoldingD]

Is that newer MAC 4K, even 5K?

And the o,der MAC 2K?

Do you have an external monitor that can be run at 2K?

[Cvatik]

They are both 15" Macbook Pro models, not using any sort of external display.