Man pages matching name pmdadso in section 3:

pmdaDSO.3.en	debian 10 / libpcp-pmda3-dev
pmdadso.3.en	debian 10 / libpcp-pmda3-dev
pmdaDSO.3.en	debian 11 / libpcp-pmda3-dev
pmdaDSO.3.en	debian 12 / libpcp-pmda3-dev