I just created a fresh install of Ubuntu 21.04 on a brand-new Pi4 - and while KStars is available in the Ubuntu Software catalog - it was NOT even close the most recent version of KStars (3.5.3). Instead it was a broken version 3.4.3 with lots of icons missing. I then tried to install from the terminal - and this time it said it couldn't find "kstars-bleeding). I tried just "kstars" and it installed - but again, the much older version.