I'll answer my own question about the logging. The settings are in lc_turnkey.xml. I modified the setting for periodic-rotating-file-handler and <logger category="com.adobe">, changing "INFO" to "DEBUG". I'm not sure if it was necessary to change both or if one would have been sufficient. I restarted JBoss and my logs became much more detailed.
Unfortunately, the detailed logs didn't help me much in figuring out what's causing the "cookies" screen to appear upon logging on to Workspace. Below are a few lines that may be relevant. I've put in bold the bits that made me think these may be relevant.
09:29:12,246 DEBUG [com.adobe.idp.um.businesslogic.authentication.AuthenticationManagerBean] (Thread-386) UserM:: [Thread Hashcode: 1475448974] Trying to authenticate against AuthProvider com.adobe.idp.um.provider.authentication.LDAPAuthProviderImpl
09:29:12,246 DEBUG [com.adobe.idp.um.provider.authentication.LDAPAuthProviderImpl] (Thread-386) UserM:: [Thread Hashcode: 1475448974] Authenticating with LDAP Auth Provider
09:29:12,246 DEBUG [com.adobe.idp.um.provider.authentication.LDAPAuthProviderImpl] (Thread-386) UserM:: [Thread Hashcode: 1475448974] Domains fetched for LDAP Authentication
09:29:12,246 DEBUG [com.adobe.idp.um.provider.authentication.LDAPAuthProviderImpl] (Thread-386) UserM:: [Thread Hashcode: 1475448974] Authenticating against LMNOP domain
09:29:12,309 DEBUG [com.adobe.idp.um.provider.authentication.LDAPAuthProviderImpl] (Thread-386) UserM:: [Thread Hashcode: 1475448974] Got DN for user langdonj
. . .
09:29:12,434 DEBUG [com.adobe.idp.um.businesslogic.authentication.AuthenticationManagerBean] (Thread-386) Authentication successful for com.adobe.idp.um.provider.authentication.LDAPAuthProviderImpl and the user is identified as langdonj . . .
. . .
begin sql[http-/0.0.0.0:8080-1] -
SELECT COUNT(*) FROM tb_cache_config T0 WHERE T0.qname = 'Replicated:UM_COOKIE_SESSION_CACHE'
09:29:12,449 DEBUG [com.adobe.pof.adapter.LoggablePreparedStatement] (http-/0.0.0.0:8080-1) 2948:. end sql[http-/0.0.0.0:8080-1, 0
. . .
09:29:12,449 DEBUG [com.adobe.idp.um.server.cache.UMCacheManager] (http-/0.0.0.0:8080-1) Using cacheType [Replicated] for Cache [UM_COOKIE_SESSION_CACHE]
09:29:12,449 DEBUG [com.adobe.idp.um.auth.filter.SSOFilter] (http-/0.0.0.0:8080-1) Successfully authenticated so redirecting to source_url?login_result=0 also added the auth cookie with Id 5AF65F09-FE4F-B55B-15A4-2A2BFE2495DE