When I was building my multiCERT app for BlackBerry 10 which adds full Let’s Encrypt trust to BB10 with just two clicks, a developer support advisor at BlackBerry confirmed to me that LE trust will be built in to OS 10.3.3. Until then you can easily import the needed certificates with my multiCERT app.
This website was previously inaccessible on BB10 without a manual certificate import because the cert was not trusted. Now it is accessible and the cert is trusted. Yay!