Hi there, I have a laptop with 8GB and dedicated NVidia GPU and I just noticed that It's saying that Garuda is saying that I only have 5.8GB usable of 8GB of Ram ... I already tried switching completely to GPU instead integrated... but this didn't solve the problem... anyone knows?
No, it's because the iGPU is reserving system RAM. It will reserve system RAM unless you switch to discrete graphics in the BIOS (or reduce the amount of reserved RAM).
It's quite possible your laptop doesn't provide those options so there's no fix - you simply have 2GB reserved and unusable, and you know not to buy the same laptop next time (or complain to the manufacturer).
I would not advise removing zram unless you have really looked into it. It is more or less regular ram with compression. Most systems benefit from it and can even eliminate using swap.