Unofficial as in autonomous and not under command of the Army.
This kind of thing -> reuters.com/article/us-ukraine-crisis-poland-militias/eyeing-russia-nervously-poles-enrol-in-volunteer-militias-idUSKBN0MG24I20150320
Reuters refer to them as unofficial "The Polish government has kept its distance from the unofficial civilian militias"
Anyway, this militia is from the Reuters report but a bit too far sjs-siedlce.pl
Also found this obronanarodowa.pl which I am busy translating "The Mazowiecka Territorial Defense training project is an initiative aimed at integrating pro-defense communities from the Mazowsze area"
So in their speak, I am looking for a pro-defense community
Not sure about the Dads army stuff but your village might have a volunteer fire brigade that has a bit of training once a week and some pretty good booze ups. One of my relatives was doing that and actually had to deal with quite a few fires over the years
Archives - 2010-2019 / Life / Polish Militia - the growth of unofficial militia groups in Poland.