upgrade to 20.04.02 not fully achieved. System works but libreoffice won't launch and icons look weird

[Mario Pagano]

ot fully achieved. System works but libreoffice won't launch and icons look weird.
As to libreoffice, my command

libreoffice --writer '*.docx'

has the following response:

(soffice:30758): Gtk-WARNING **: 11:06:58.558: Theme parsing error: gtk.css:1566:23: 'font-feature-settings' is not a valid property name

(soffice:30758): Gtk-WARNING **: 11:06:58.562: Theme parsing error: gtk.css:3618:25: 'font-feature-settings' is not a valid property name

(soffice:30758): Gtk-WARNING **: 11:06:58.563: Theme parsing error: gtk.css:4080:23: 'font-feature-settings' is not a valid property name
==== AncientGreek (autoload.py) : Executing AncientGreek.modAccelerator.InitProgram
Application Error.

which is also true for other softwares like calc, impress etc

ProblemType: Package
DistroRelease: Ubuntu 20.04
Package: mpich 3.3.2-2build1
ProcVersionSignature: Ubuntu 5.4.0-80.90-generic 5.4.124
Uname: Linux 5.4.0-80-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.18
Architecture: amd64
CasperMD5CheckResult: skip
Date: Mon Aug 2 19:19:52 2021
ErrorMessage: tentata sovrascrittura di "/usr/bin/mpicc.mpich" presente anche nel pacchetto libmpich-dev 3.3~a2-4
InstallationDate: Installed on 2018-02-15 (1264 days ago)
InstallationMedia: Ubuntu 17.10 "Artful Aardvark" - Release amd64 (20180105.1)
Python3Details: /usr/bin/python3.8, Python 3.8.10, python3-minimal, 3.8.2-0ubuntu2
PythonDetails: /usr/bin/python2.7, Python 2.7.18, python-minimal, 2.7.15~rc1-1
RelatedPackageVersions:
 dpkg 1.19.7ubuntu3
 apt 2.0.6
SourcePackage: mpich
Title: package mpich 3.3.2-2build1 failed to install/upgrade: tentata sovrascrittura di "/usr/bin/mpicc.mpich" presente anche nel pacchetto libmpich-dev 3.3~a2-4
UpgradeStatus: Upgraded to focal on 2021-08-02 (0 days ago)