With a PC connection and adb, I can install packages by running
adb install foobar.apk
There is also an option to downgrade a package to an earlier version and keep data (as long the app itself did not introduce any incompatibilities in the later version):
adb install -r -d foobar.apk
Is there an equivalent local command which I could run from a terminal session (or any other way to downgrade without a PC connection)?