How to update the Breton flag in the online LT checker?

Hi. When selecting the online Breton grammar checker at the flag being displayed is the French frag. It’s not ideal. How can we change it to the Breton flag? I.e. this flag: Flag of Brittany - Wikipedia

I already see a Breton flag icon in the LT repo at:

But somehow that icon is not used on the website and I don’t know where the repo of the website is located to attempt to correct it.

The Breton flag is admittedly a bit complex to be rendered at such tiny size.
An alternative flag is the “Kroaz Du” flag (= Black Cross) Kroaz Du - Wikipedia which is simpler, so possibly more suitable for such a small icon. But the available br-FR.png icon may be fine too.