I just installed the 12.8 on our server and fired up the WebCenter page (https:\\ [server ip]:4130). The language for everything is English except the search dialog, which is French.
Can I change this page language to English?
Interesting. Firefox 98.0.2 has the page in English, Chrome 99.0.4844.82 is English, Edge 99.0.1150.46 and 1150.52 displays it in French.
I'm going to blame this on Edge.
The page will show whatever localization your browser presents. If it presents none, it'll show English. (This is true for other pages like the SSLVPN splash, too.)
WatchGuard Customer Support
I figured as much. The curious item is that the localization is English (US) and all the other WebCenter pages are English except for the search page. Cleared the cache and it still happens. I'm not going to worry about it, I've got two other browsers to choose from that work fine.
Everything on WebCenter 12.8 is in English on my Edge version 99.0.1150.55