I checked to see if there were any Joplin packages in there a while ago when writing Unofficial alternative Joplin distributions but didn't find any.
Ultimately (at least currently) the team only maintains a single Linux distribution for both the desktop and terminal clients (appimage for the former, node package for the latter). All of the other distributions are community maintained and if somebody creates and is maintaining a package on pacstall then feel free to add it to the wiki post linked above.