Those do not sound like issues that most people are encountering. I’ve been using Plasma 6.0 from the first release and Dolphin right-click options are definitely there.
So I think it’s most likely that something went wrong when upgrading from your 5.27 release. Unfortunately not every Plasma component had a comprehensive update/migration and some customizations need to be set up again from scratch.
For Dolphin service menus (the additional options that some people install on top of the regular menu), I remember there was a thread about how to migrate your custom menu entries to Plasma 6. But maybe that’s not what you’re talking about. Hard to tell from the brief description.
I suggest you try creating a new user account on the same system, and compare that against your existing account. That way you can tell which issues are caused by bugs in the applications themselves, and which issues are caused by buggy config migration.