I’d like to remind everyone that the purpose of this topic, and meaning of the original post is NOT:
“Hey, Sailfish OS 5.1 has been released, everybody hurry up and install it!”
rather it’s:
“We have a build environment available at OBS which you, if you are a developer, and if you want to prepare your apps for the upcoming release, can use to do it.
And as you would want to test whatever you built, here’s a hint that you can upgrade to the currently semi-closed-BETA, DEVELOPER-ONLY PREVIEW of Sailfish OS 5.1”.