You need the Update 1.0.2 specifically bundled with the title.key that matches the Rebuilt NSP. Here is the checksum theory (do not use illegal hash sites, but verify your file structure):
Lego City Undercover patch is out and it's 479MB : r/NintendoSwitch. lego city undercover switch nsp update patched
Place both the LEGO City Undercover base NSP and the corresponding update NSP onto your SD card or prepare them for USB installation. You need the Update 1
Since its 2017 launch, several patches were released to stabilize the experience. While TT Games rarely released detailed public patch notes for these updates, community analysis and technical tests highlight the following changes: Version 1.0.1 (Day One Patch): lego city undercover switch nsp update patched