There is now a score of Van der Pals' cello sonata no.1 op.5a in D minor (1905-6) available at ISSUU (https://issuu.com/scoresondemand/docs/leopold_van_der_pals_sonata_for_cello_and_piano_op), and the work is: available on YouTube (playlist) (https://www.youtube.com/playlist?list=OLAK5uy_m-PApd1yUgR8JvFCHyLjyXhb54pwZnJ50) and was performed (I presume that "cello sonata in D minor" is the same work) in Copenhagen back in March 8th and/or 17th 2024. The cellist, who looks to be a relative of the composer, mentions that this or a slightly earlier performance is a world premiere; there's a CD with another cello sonata of the composer, his Op.48, which I had not noticed but I assume is fairly recent. I seem to recall his orchestral efforts - concertos, symphony - have met with mixed reviews here but maybe he was more successful with chamber forces- has anyone heard any of these works?
The two van der Pals Cello Sonatas are featured on this webpage:
https://gatewaymusicshop.dk/da/idxsearch?text=van+der+pals