I solved the problem by uninstalling the packages dca-enabler and dca-enabler-packages. See here .
I got a precision 3450 last week with ubuntu 20.04. I immediately upgraded the system to 21.04, but ran into the problem described here , that after a seemingly successful upgrade, the OS doesn't realize that it's at the new version, and therefore e.g. shows incorrect info when queried with 'lsb_release -a' and in particular refuses further upgrades. I traced this problem back to the file /usr/lib/os-release -- which contains version info -- not being upgraded for some reason. The file is part of the package base-files, which is replaced with a new version during the upgrade, but for some reason the upgrade process does not upgrade this specific file even though it's in the package in a new version. I assume this is due to some Dell-specific modification in the pre-installed Ubuntu version? In any case, I managed to solve the problem by over-writing /usr/lib/os-release by hand with the new version. After this I repeated the process and upgraded to 21.10. My first question: I realize that over-writing /usr/ib/os-release by hand is a hack. Is there a better way to upgrade? Or is Dell deliberately blocking this? Anyway, the system is running fine now, except for one problem: when I enter 'curl' on the command line, I get the error message > curl: error while loading shared libraries: libldap_r-2.4.so.2: cannot open shared object file: No such file or directory This looks like a problem with shared libraries for me. I asked a friend who is running Ubuntu 21.10 on a XPS 13 and has the same versions of curl and libldap, and curl works fine for him. Googling the error message doesn't give any hits, so it seems to be specific to my system. I wonder if it's due to the 'hacky' way that I performed the upgrade, and whether that messed up something with the dynamic linker. But surprisingly, everything else works and I'm running a KDE destkop, chrome, and vscode. Did anybody see anything similar? What can I do to fix curl? And is there some deeper problem in my installation due to the hacky upgrade?  
curl problem after ubuntu upgrade