MatPy's questions

I just upgraded to Ubuntu 20.04 and wanted to try the Deepin Desktop Environment which looks great. I added the PPA (ppa:leaeasy/dde) to the known repositories as recommended. But there are some dependencies that cannot be resolved when trying apt install dde.

The package qtbase-abi-5-9-5 cannot be installed: It looks like to be a virtual package that points to libqt5core5a which is already installed. The real package is installed but the virtual package is not referenced as installed.

This library is used by Plasma and many others so I don't really want to uninstall/reinstall it with the virtual package.

Is there an easy workaround to get the qtbase-abi-5-9-5 package "installed" or bypass this dependency when installing DDE?

EDIT: apt-cache policy dde

  dde:
  Installed: (none)
  Candidate: 15.4+16
  Version table:
     15.4+16 500
        500 http://ppa.launchpad.net/leaeasy/dde/ubuntu bionic/main amd64 Packages
        500 http://ppa.launchpad.net/leaeasy/dde/ubuntu bionic/main i386 Packages

I am using Ubuntu 18.04 and since few weeks (I cannot say when exactly), my system is experiencing freezes when there are disk I/Os.

My system is installed on an ext4 partition of a SSD.

Even if the load is not very high, some short freezes occur, mouse moves are no longer smooth, Plasma is responding slowly, apps are often in "waiting for disk" state.

This happens for any kind of disk use : software launches, file transfer. When the system starts swapping, it becomes almost unusable.

There is no error in SMART report and I am using Windows on the same disk without anything comparable, so it should not be a hardware problem.

I have checked the partition offset and changed the IO scheduler (https://blog.vacs.fr/index.php?post/2010/08/28/Solving-Linux-system-lockup-when-intensive-disk-I/O-are-performed), and it remains the same.

I have the impression that it is linked to the interruptions management, but I don't know how to check that.

I am now running out of ideas and I hope you may help!

EDIT:

sysctl vm.swappiness

vm.swappiness = 60           #default

free -h (at startup)

              total        used        free      shared  buff/cache   available
Mem:           3.8G        780M        1.6G        117M        1.4G        2.6G
Swap:          3.7G          0B        3.7G

I found a repeatable way to create this freeze with a partition scan with GParted. At startup there is no problem but freezes seem to appear when the first bytes are written on swap. I am checking my swap configuration.

EDIT 2:

The problem appears very quickly. With this memory usage, it is already freezing:

              total        used        free      shared  buff/cache   available
Mem:           3.8G        1.7G        530M        267M        1.5G        1.5G
Swap:          3.7G         48M        3.7G 

I was trying to add a PGP key for non-Ubuntu packages when I realized that any apt-key request is doing nothing (no output, no configuration change) and the program exit with code 2, except for --usage.

How can I fix it? Is there a debug output file of apt-key? Or in last case, is there a way to reinstall easily apt/apt-key without destroying my current configuration?