Here's my code for converting tsv data from database to QuickStatements: https://github.com/yarl/wlm-poland-to-wikidata (not finished of course).

First upload using script:
https://www.wikidata.org/wiki/User:Polish_Monuments

https://www.wikidata.org/wiki/Q29867168
https://www.wikidata.org/wiki/Q29867186

Comments will be useful.

The one thing which could be good is a P854 and a P577 in the reference. The P854 would make it easier to verify and the P577 would give some indication of how relevant the source is (in a few years time when everything has changed ).

Is the protection further subdivided by types? (E.g. there is a distinction between listed buildings and archaeological sites). Wondering since Q21438156 sounds quite high-level (but that might just be the English label and my bias for how things are subdivided in Sweden).

In T158569#3254450, @Lokal_Profil wrote:

Is the protection further subdivided by types? (E.g. there is a distinction between listed buildings and archaeological sites). Wondering since Q21438156 sounds quite high-level (but that might just be the English label and my bias for how things are subdivided in Sweden).

According to https://pl.wikipedia.org/wiki/Zabytki_w_Polsce, there are three sub-types: immovable monuments (buildings or their parts), movable monuments (eg. art collections) and archeo monuments. But the WLM data only covers the first type. Not sure whether the register number has a similar form for the other groups.

If I see correctly, database dump is from March 8, I can add it.
Regarding P854: I think I will add it to P2186 (WLM ID), it's kinda overkill to add it to every statement. Especially some of them are computed/derivated form form of data stored in database.

I've created entries for immovable and movable monuments to be more specific. I will use it to import future entries.
https://www.wikidata.org/wiki/Q29940414
https://www.wikidata.org/wiki/Q29940621

In T158569#3254497, @Alicia_Fagerving_WMSE wrote:

Not sure whether the register number has a similar form for the other groups.

No idea. But they are out of scope right now.