Well, it seemed promising, but when I clicked “view site” to go back to the main index page, it crashed. 
From the php-fpm log:
[27-Feb-2025 15:21:37 UTC] PHP Fatal error: Uncaught Error: Call to undefined function WPDiscourse\Shared\mb_convert_encoding() in /wordpress/wp-content/plugins/wp-discourse/lib/template-functions.php:335
Stack trace:
#0 /wordpress/wp-content/plugins/wp-discourse/lib/discourse-comment-formatter.php(136): WPDiscourse\DiscourseCommentFormatter\DiscourseCommentFormatter->fix_avatars_in_quotes()
#1 /wordpress/wp-content/plugins/wp-discourse/lib/discourse-comment.php(312): WPDiscourse\DiscourseCommentFormatter\DiscourseCommentFormatter->format()
#2 /wordpress/wp-content/plugins/wp-discourse/blocks/comments/comments.php(34): WPDiscourse\DiscourseComment\DiscourseComment->comments_template()
#3 /wordpress/wp-includes/class-wp-block.php(537): render_block_wpdc_comments()
#4 /wordpress/wp-includes/class-wp-block.php(517): WP_Block->render()
#5 /wordpress/wp-includes/class-wp-block.php(517): WP_Block->render()
#6 /wordpress/wp-includes/blocks/post-template.php(123): WP_Block->render()
#7 /wordpress/wp-includes/class-wp-block.php(537): render_block_core_post_template()
#8 /wordpress/wp-includes/class-wp-block.php(517): WP_Block->render()
#9 /wordpress/wp-includes/class-wp-block.php(517): WP_Block->render()
#10 /wordpress/wp-includes/blocks.php(2191): WP_Block->render()
#11 /wordpress/wp-includes/blocks.php(2243): render_block()
#12 /wordpress/wp-includes/block-template.php(263): do_blocks()
#13 /wordpress/wp-includes/template-canvas.php(12): get_the_block_template_html()
#14 /wordpress/wp-includes/template-loader.php(106): include('...')
#15 /wordpress/wp-blog-header.php(19): require_once('...')
#16 /wordpress/index.php(17): require('...')
#17 {main}
thrown in /wordpress/wp-content/plugins/wp-discourse/lib/template-functions.php on line 335
Edit1: It says undefined function mb_convert_encoding(). Maybe I just need to install a missing PHP package?
Edit2: Yep, that’s all it was. I needed to install php-mbstring. Everything seems to be working now. Thanks!