Is there any way to filter only lncRNA gene IDs from the output of featurecounts? And would it be relevant to use the values (counted with gene id) in the DE analysis of lncRNA?
You can use gene-level raw read counts for DE.
For the lncRNA list, you may subset the expression dataset rownames (suppose to hold ENSG ids) by the gene biotype. To do so use biomaRt to find biotype for each gene, then only retain lncRNA.
Some lincRNA is in the Ensembl gene model, and they are structurally similar to mRNA. So they might have already been quantified in the mRNA quantification data
You can use gene-level raw read counts for DE. For the lncRNA list, you may subset the expression dataset rownames (suppose to hold ENSG ids) by the gene biotype. To do so use
biomaRt
to find biotype for each gene, then only retain lncRNA.