Due to this post the Librem 5 will have the same size as the Samsung Galaxy S10e has which isn’t useful for a case at all but maybe for the screen protector glass. The screen protectors might fit, which would be as important as a case for me. For the second case mentioned in this post the Huawei P9 screen protectors could be a good choice…?
Or is there already an other idea where to get a screen protector from?