Can not save post with Wordpress on Docker
.htaccess should not have effect in your wordpress install because you are using Nginx.
Refer these posts to configure correctly your Nginx instance. There are several recipes depending if you are using HTTPS or not, cache plugins, etc.
You are having redirect loop since you proxy to http on Wordpress container, but configured Wordpress to work on https.
for your configuration, please add following to your wp-config.php before the happy blogging line to resolve it:
if (isset($_SERVER['HTTP_X_FORWARDED_PROTO']) && strpos($_SERVER['HTTP_X_FORWARDED_PROTO'], 'https') !== false) { $_SERVER['HTTPS'] = 'on'; }/* That's all, stop editing! Happy blogging. */