The built in WebKit engine was perhaps a bit out there, but besides Mozilla there was also Opera who had been doing mobile browsing for quite some time (Opera Mobile originated on Windows PocketPC).
You beat me to it. Opera was a good example that they could've cut OEM deals as a mobile browser.
Yup, but the surge of iOS and Android quickly brought that to an end, there is almost no OEM deals at mobile. (Still exists at TV/Set-top boxes, but those are not nearly as popular.)