Plastikina will release the new album "Maa" from Finnish a cappella act Rajaton on October 10. Many of the texts have roots in Finnish folklore as well as poets such as Eino Leino, P. Mustapää and Katri Vala. Check out soundclips: https://www.musicmakers.fi/plastinka/rajatonreleases.php
RIYL Värtinnä and the like, though some tracks seem to be closer to typical modern a cappella than folk (I far prefer the latter).