I am working on several themes from the Crip Zone. Two are only updated so far but I am working to update all of them for 2.1 Gold.
You can see them on our demo board for 2.1 here:
https://www.jpr62.com/demos21/index.php
Just use the "Theme Select" block on the top left to choose a theme.
The theme Clean white is not working well with SMF 2.1 RC2.
When I open some topic with replies, I see only first post, and after it, I get error message:
Fatal error: Uncaught Error: Call to undefined function template_quickbuttons() in /home/bulataka/public_html/test/Themes/default/Display.template.php:865 Stack trace: #0 /home/bulataka/public_html/test/Themes/default/Display.template.php(255): template_single_post(Array) #1 /home/bulataka/public_html/test/Sources/Load.php(2494): template_main() #2 /home/bulataka/public_html/test/Sources/Subs.php(3467): loadSubTemplate('main') #3 /home/bulataka/public_html/test/index.php(154): obExit(NULL, true, true) #4 {main} thrown in /home/bulataka/public_html/test/Themes/default/Display.template.php on line 865
Click =>

All the next posts in topics are not shown.
Version Information:
Forum version: SMF 2.1 RC2 (more detailed)
Current SMF version: SMF 2.1 RC2
GD version: bundled (2.1.0 compatible)
MySQLi engine: MySQL
MySQLi version: 5.5.62-cll
PHP: 7.3.7 (more detailed)
Server version: Apache