SOLVED
I solved this on another post, below is the text of that post.
https://forum.lazarus.freepascal.org/index.php/topic,41264.msg287107.html#msg287107FINALLY..I now seem to have a solution for this irritating problem.
I hope this helps those still unable to add packages. This is my solution.....
1 Open a terminal with CTRL-ALT T
2. In the terminal start Lazarus with "sudo startlazarus"
3. From the top line menu select Package | Open loaded package
4. Scroll down the list of packages and open LazControlDsgn package
5. When the package window opens, Click on " Compile" on the top line if the window
6. Then click "Use" (next to compile) and select install. (This is very important to do)
7. From the "Tools" menu on the top line menu, select "Build Lazarus with Profile: Normal IDE"
And that should do it !!
Lazarus should then build and find the LazcontrolDsgn compiled package. Once the IDE is built, shut down Lazarus and the terminal and re-start Lazarus normally.
Now you should be able to add other packages and rebuild the IDE like previously. The only problem that I've noted is that Lazarus does not re-start automatically after the rebuild.
You don't have to use "sudo" to start Lazarus again. I suspect that the original problem might have been a permissions issue in lazarus not finding the compiled LazControlDsgn compiled unit, so (possibly ?) using "sudo startlazarus" the first time allowed the compiled unit/package to be saved in a protected directory? Only a guess.
Now...how to allow Lazarus to re-start automatically after rebuilding the IDE ???
HTH.
Laurie