(I use Steam)
Both Steam and non-Steam Blockland installations use the same file hierarchy.
Files on a Steam installation can be found in the same location as in a non-Steam installation.
banlist.txt does exist, however auto admins are stored in prefs.cs, not adminlist.txt.
Both banlist.txt and prefs.cs can be found in
<location of steam games>\Blockland\config\server.