Script that can copy subtitles from /Subs or /Subtitles folders to parents, so that Plex can work with them. (https://www.reddit.com/r/PleX/comments/fpp2f2/any_way_to_have_plex_use_the_subs_folder_or/)

Rename-Subtitles.ps1

param(
    [Parameter(Mandatory=$true)]
    [string]$PathToMediaFolder
)

function Copy-IfLarger {
    param(
        [Parameter(Position=0, Mandatory=$true)]
        [string]$sourceFilePath,
        [Parameter(Position=1, Mandatory=$true)]
        [string]$targetFilePath
    )

    $sourceSize = (Get-Item -LiteralPath $sourceFilePath).length
    $targetExist = Test-Path -LiteralPath $targetFilePath
    $targetSize = if ($targetExist) {(Get-Item -LiteralPath $targetFilePath).length} else {0}
    if ($sourceSize -gt $targetSize) {
        Write-Host "Copying $sourceFilePath to $targetFilePath"
        Copy-Item -LiteralPath $sourceFilePath $targetFilePath
        if ($targetExist) { Write-Host "Replaced existing subtitle since new subtitle was larger than existing" }
    } else {
        Write-Host "Didn't copy $sourceFilePath due to existing subtitle being bigger or if same size"
    }
}
function Copy-Subtitles {
    param(
        [Parameter(Position=0, Mandatory=$true)]
        [System.IO.DirectoryInfo]$SourcePath,
        [Parameter(Position=1, Mandatory=$true)]
        [System.IO.DirectoryInfo]$TargetDir,
        [Parameter(Position=2, Mandatory=$true)]
        [System.IO.DirectoryInfo]$Name
    )
    Write-Verbose "Beginning copy of subtitles from $SourcePath"
    $files = (Get-ChildItem -LiteralPath $SourcePath -File)
    Write-Verbose "Found $($files.length) files"
    foreach($file in $files) {
        Switch -Regex ($file.name) {
            'Swe' {
                Write-Host "Found Swedish Subtitle"
                $new_name = Join-Path $TargetDir "$($Name.Name).sv$($file.Extension)"
                Copy-IfLarger $file.FullName $new_name
            }
            'Eng' {
                Write-Host "Found English Subtitle"
                $new_name = Join-Path $TargetDir "$($Name.Name).en$($file.Extension)"
                Copy-IfLarger $file.FullName $new_name
            }
            'Romani' {
                Write-Host "Found Romanian Subtitle"
                $new_name = Join-Path $TargetDir "$($Name.Name).ro$($file.Extension)"
                Copy-IfLarger $file.FullName $new_name
            }
        }
    }
}

if (-not (Test-Path -LiteralPath $PathToMediaFolder)) {
    Write-Error "This path does not exist. Please double check it."
    exit 4
}

if (Test-Path -LiteralPath "$($PathToMediaFolder)/Subs") {
    Write-Verbose "Found Subs folder."
    $directory = Join-Path $PathToMediaFolder "/Subs"
} elseif (Test-Path -LiteralPath "$($PathToMediaFolder)/Subtitles") {
    Write-Verbose "Found a Subtitles file"
    $directory = Join-Path $PathToMediaFolder "/Subtitles"
} else {
    Write-Verbose "Found no subtitle folder within $PathToMediaFolder"
    exit 0
}

$folders = Get-ChildItem -LiteralPath $directory -Recurse -Directory | Where-Object({$_.GetFiles().Count -ne 0})
Write-Verbose "$($folders.Count) folder(s) have been found."
Write-Verbose "Beginning Copy of Subtitles."
if ($folders.Count -gt 0) {
    foreach($subfolder in $folders) {
        Copy-Subtitles -SourcePath $subfolder -TargetDir $PathToMediaFolder -Name $subfolder
    }
} else {
    Copy-Subtitles -SourcePath $directory -TargetDir $PathToMediaFolder -Name $PathToMediaFolder
}

Write-Verbose "Script has been completed & Plex can now read these files."

cannot get this to work on Windows. When I remove the functions and run the raw code it keeps telling me LiteralPath is null. Any ideas?

Example usage, with fd utility to search through a disk/path:

fd Subs --type directory /mnt/media/ -x pwsh ~/path-to/Rename-Subtitles.ps1 {//} -Verbose