Thank you so much! I deleted everything and tried with your code and it worked. And, based on your code, I rewrote the whole thing. I'll paste it below for any other users looking for it, as it is working.
<IfModule Litespeed>
# Block access to readme.html and readme.txt files
RewriteCond...
Hey guys!
I got a VPS with Ubuntu 20.04, Cyberpanel and OpenLiteSpeed, and launched a WordPress website there. All good, up until I realized /xmlrpc.php was not blocked/denied (despite having implemented code in .htaccess for it).
I checked the code and rewrote it accordingly to OLS, no dice...