Reclaiming RAM after GPU VRAM allocation is too high

I have a mid-2011 Macbook Air with 4 GB of RAM. I used OpenCore to successfully install Monterey on it. However, soon I realized that it patched also the BIOS, and the GPU now allocates 800+ MB of RAM on the EFI BIOS, while previously, by default, it was allocating only 384 MB. This has a significant impact on my Linux partition, as it likes enough RAM to work correctly. You see, after whatever OpenCore did, it does NOT dynamically allocate VRAM as needed, it got hardcoded in the BIOS, so when the Linux kernel boots, it sees that amount of VRAM as "reserved" and won't use it for anything but GPU stuff.

Unfortunately, un-patching does NOT reallocate the extra 400MB of VRAM back to the main RAM. How do I reclaim that extra RAM? I need the RAM to be at 3.7 GB (as it was before), while after the patching now Linux reports 3.24 GB. Please note, this happened only after OpenCore installed Monterey and patched the BIOS. It was not an issue before OpenCore/Monterey.

I'm willing to lose Monterey/MacOS to reclaim the extra RAM btw. That laptop is RAM-hungry at 4 GB and I can't afford to give more to the GPU.

Any ideas on what to do?