This (and the screenshot above from SMPlayer) simply indicate the Blu-ray disc is being opened as a DVD (likely because of missing Blu-rays support) - which of course does not work. The whole /VIDEO_TS folder simply does not exist on Blu-rays at all - they use a different folder/file structure than DVDs.
The how-to linked in the second post is actually the best I found on this topic so far, yet the key takeaway mentioned there is "How to Play (Some) Blu-rays on Linux with VLC".
The linked key database does not seem to contain the ones needed to play those particular discs. Trying others which are listed there might work but it's definitely very hit-and-miss on Linux.