Well I haven't watched any of these 3 anime yet but to attempt to answer your question, google says a part two of Sakamoto Days is scheduled to air in July 2025 so the anime isn't finished yet and that's probably why it ends in a cliff hanger. For Beastars the third and final season is split up into two parts "Final Season Part 1" and Final Season Part 2" the former of which aired in December recently and the latter has not yet aired so Beastars isn't fully finished airing either. For Dandadan google says Season 2 is scheduled to air in the summer of 2025 and the Manga isn't done either so the plotline of Dandadan isn't fully finished as well.I finished watching episode 11 of Sakamoto Days and was kind of disappointed that the ending left off in a cliff hanger. Not even that, it felt like it left off in the middle of an episode.
Has this always been a thing? I remember being disappointed with the ending of Dandadan and season 3, part 1 of Beastars because they did something similar.
Hope this helps, like I said I haven't had time to actually watch any of these anime yet though Beastars has been on my watchlist for a while.