wloot I want to know whether the flarum official is still providing support for old browsers.
From a security perspective, using older browsesr and expecting websites etc to work with them is not going to work as standards such as SSL and TLS improve. These browsers often contain weak ciphers which most web pages will not work with anyway when you try to connect to the site.
I suppose Flarum could add a banner across the top of the page that looks for older browser versions and issues a warning, but that's at the dev's discretion.