SOLVED
Turns out, because I'm using the ListEscape Dovecot plugin, my delimiter is $ not . I figured this out by connecting directly via openssl s_client and running a LIST command.
So, I edited the config.inc.php file and hard set the delimiter to '$'. Thank you SKaero for talking about making the changes there, because it turns out there was a delimiter line in there that was telling RC it was '.'. I modified that to be '$' and it started working correctly. However, that worked for the main login, but not the additional_imap plugin.
Additional_IMAP Solution:
To resolve this, first I tried editing the config and various php files to modify the delimiter, but nothing worked. Then I remembered that this plugin creates SQL tables and stores its data in the db. So, I logged into postgres and did the following:
select * from additional_imap;
This returned a record that showed a delimiter of "." in the preferences column. So, I changed it.
update additional_imap set preferences='a:9:{s:21:"show_real_foldernames";b:1;s:20:"lock_special_folders";b:1;s:11:"drafts_mbox";s:6:"Drafts";s:9:"sent_mbox";s:0:"";s:9:"junk_mbox";s:0:"";s:10:"trash_mbox";s:0:"";s:12:"archive_mbox";N;s:24:"sticky_notes_imap_folder";N;s:14:"imap_delimiter";s:1:"$";}' where id='2';
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Bottom line is that Roundcube should really be able to detect the $ delimiter as every other webmail solution I've tried handles it just fine (NextCloud, Squirrelmail, etc.).
Also, additional_imap needs an additional delimiter option of $ so that can be selected in the drop down list when configuring an additional imap account.
The good news is that it's all working now.