Halcek Unfortunately Joplin (I've used it on Android btw), will not be included on Solus because it's been rejected per the package inclusion policy. You may view the now closed tasks over here - https://dev.getsol.us/T7667 and here - https://dev.getsol.us/T6488
Apparently someone may have gotten an app image of Joplin working, I'm not able to confirm that myself though.
As for Manuskript, over here https://dev.getsol.us/T765 it's development has been slow, but still doesn't have a stable formal release, so that isn't going to be included in the repos either. Now if these developers of these applications ever made a snap or flatpak you'd be in a better place I'm sure, but in the meantime Solus does have many alternatives to these applications that are current, up to date, and meet the standards set forth by the Solus inclusion policy.
Now how did I find all this stuff out exactly? Well, it's rather simple! If you head over to https://dev.getsol.us/ you can use the search field in the top right and look up any application to see if there is already a task for it or not. If there is a task for one you can read up on the latest comments, and if there isn't a task then you may feel free to create one. In this particular case, someone before you had already put out a task for these applications so the work is already done and taken care of so to speak. Hope this helps answer your question and clears a few things up!
