This simple extension increases your forum's title limit to 180 as 80 characters are sometimes less.
This is not written by me, I was afraid to modify core files and I made this, OFFICIAL Source https://discuss.flarum.org/d/27623-extending-post-size-in-flarum-1x
composer require ramesh-dada/flarum-increase-title
composer update ramesh-dada/flarum-increase-title
composer remove ramesh-dada/flarum-increase-title