montuos

Still present in 1.16.1.  Player posted about it in r/MinecraftHelp; tried it myself in a new world.  Seed 5488762045858212, coordinates -350, ~, -1565, went spectator and searched the entire area from sea level to bedrock, and found nothing resembling a ruined portal.

This bug is extremely frustrating.  If the launcher knows there is a new version, it should link to a place where I can download that version, instead of exactly the same version I already have installed.

Same thing here.  I finally turned off "Update to Beta versions" so it would stop telling me to update to the version I already had.

Additionally, today I saw in the wiki that 2.1.3514-beta is available as of 2019-04-09, but even with "Update to Beta versions" re-enabled, "click here" still sends me to the normal download page with Minecraft.deb for 2.1.2482.  It doesn't offer any way to get to the beta, new or otherwise.

I came to report that my spider and skeleton spawners were no longer working in 18w20a, but this bug report could easily be the explanation for that.

I too updated my world from 18w16a.  I've been switching back and forth between survival at normal difficulty and creative mode.  Either way, the spawners don't spawn anything.  My base and caves are well lit, verified with spectator mode, so there aren't any hidden underground mobs maxing the mob cap.