Granted, the warning says clearly “If you deselect Undetermined, you will not see most content”, which places the onus on the individual user, as apposed to logic built into Lemmy on which posts/comments can be viewed, while also leaving it to each user to have to weed out alternate languages for their views which are incorrectly set. This is indeed leading to many posts simply not appearing (as designed and intended), which is less than ideal when trying to grow a user base/community.
ctl + click or shift + click are pretty standard for selecting multiple things, yes – but not to apply those selections. Even if I select everything on the entire list and then click save, there is no way to determine that my choices have actually been applied. The list looks exactly the same as when I first set up my account.
I’ve tried double clicking items out of curiosity, but it still looks the same.
When you select them they should be highlighted. For me, I see them with a grey highlight at first, then when I’m selecting them (when the window is active) the highlights are blue.
You then have to click save at the bottom to apply the change.