Hi,
The flatpak for the most recent build can always be found at https://benpfaff.org/~blp/pspp-master/latest-org.gnu.pspp.flatpakref
Just a short question... I am using Ubuntu and the default PSPP version in Snap (which is the official Ubuntu package installing system) is 1.6.2.
Maybe it would be good to contact them to update PSPP more reguraly... Regards, Matej