Here is my quick reference guide to htaccess and the many things you can do to make your server a little more efficient, not all but the ones most users can apply on their servers for security, re routing and many other things.
This is not to fix problems that you may have with your Flarum installation
Is a quick reference guide to the many configurations available on the server and that can be set via the htaccess file to overwrite the defaults.
I mainly use it to speed up my sites setting expire headers and compression to use gzip to make files smaller. There are other sections there for security and re routing that are useful.
Be careful when applying any configuration as many share hosts may not allow you to set them.
Also be careful since not all the configurations may play nice with Flarum
Do this at your own risk
Apply only what you need and one configuration at a time, watch out for miss configuration errors by your server if you encounter such errors remove the last configuration you applied. Most of the time this errors may happen because your host may not allow setting or overwriting such configurations.
https://github.com/phanan/htaccess