I have a table of RPM data for gene expressions of all human genes in two groups of patients. (each group includes several samples)

I am going to use DESeq2 to explore if there is any gene whose expression significantly changes between two groups.

DESeq2, however, seems like accepts only nu-normalized counts for the RNA seq. Is there a way to feed the DESeq2 with RPM data?

Not really. If you don't have access to the counts or quantification data, I would not recommend to use DESeq2.

thank you for clarification!