Help with "fromFilePairs"

[NenBarto]

Good day,
I'm getting stuck with connecting processes through "fromFilePairs" and any help would be greatly appreciated.
There are two processes, one downloads locally fastq files (DOWNLOAD) and the second (FASTQC) is supposed to perform fastqc on them. I am not sure how to connect the two with "fromFilePairs". If I just pipe from one to the other, then I receive "Input tuple does not match input set cardinality declared by process FASTQC" as expected. The code below fails with "No signature of method ... is applicable for argument types: values... So either the format of the DOWNLOAD.out or the output of DOWNLOAD have to be changed, but not sure how.
Thanks a lot for your time!
N.

#!/usr/bin/env nextflow     
nextflow.enable.dsl=2

param.run="test"
params.outFastQC = "results/fastQC/"+params.run

workflow {
    RUN=Channel.of(params.run) 
    DOWNLOAD(RUN)
    Channel.fromFilePairs(DOWNLOAD.out,flat:true).set{dwnld_channel}
    FASTQC(dwnld_channel)
}

process DOWNLOAD{
     input:
        val RUN
    output:
        path("raw/$RUN/fastq/*R{1,2}*.fastq.gz"), emit: download_out 
    script:
    """
    Rscript $projectDir/1.download.R --run_id $RUN
    """
}

process FASTQC{
    publishDir("$projectDir/${params.outFastQC}", mode: 'copy')
    input:
        tuple val(sample_id), path(reads)
    output:
        path( "*_fastqc*" ), emit: fastqc_out
    script:
    """
    fastqc ${reads} 
    """
}

[NenBarto]

This issue is the same as "#2889".
One needs to map and groupTupple since fromFilePairs is not an operator. Wish it was. :D