HenBagle has released a mod that aims to completely remove mouse acceleration from the first Mass Effect Remaster. Thus, you can use this mod only for Mass Effect Legendary Edition, and not for the original/vanilla version.
As the HenBagle noted, this mod modifies the movement script to disable acceleration, as well as disabling the bEnableMouseSmoothing option. Moreover, this mod should be compatible with most other LE1 mods as it uses the new merge format to make edits.
You can download the mod from here. In order to install, you’ll have to also install ME3Tweaks Mod Manager version 7.0. Once installed, you can simply drag and drop the .7z file into the Mod Manager window, import, and then install it.
As a bonus, here is a camera mod for the entire trilogy. Created by modder Jade, this camera mod changes the Gameplay Field of View to an FOV of your choice for the entire Trilogy.