I have strange problem with file uploads and saving configuration under Joomla. Folders cannot be created with error: Warning: Failed to change file permissions!
By default all folders are 777 under WSL, apache2 directives are set as follows:
<Directory /mnt/d/www/joomla>
Options Indexes FollowSymLinks
AllowOverride All
Require all granted
</Directory>
Under folders permissions I have set owner of the directory to the one I'm logged in, also set full access for other users. Directories are all Read only but I've found out that's correct and even uncheck it will get back to checked.