SUMMARY
Installing KMail will and does remove installed mysql 8 and every already existing users and access to databases and tables!

STEPS TO REPRODUCE
1. install kubuntu 22.04 LTS
2. install mysql 8 by Percona or Oracle
3. create multiple different users, databases and tables
4. then install kmail

OBSERVED RESULT
Lost access to every database, tables and users!

EXPECTED RESULT
Should us any existing mysql server of version 8.x+ and mariadb 10.6+
or
Import every user, database and tables!

Deleting any users, databases and tables is absolutely unacceptable!

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Kubuntu 22.04 LTS 
KDE Plasma Version: 5.24.7
KDE Frameworks Version:  5.92.0
Qt Version: 5.15.3

ADDITIONAL INFORMATION

# apt install kmail
Paketlisten werden gelesen… Fertig
Abhängigkeitsbaum wird aufgebaut… Fertig
Statusinformationen werden eingelesen… Fertig
Die folgenden Pakete wurden automatisch installiert und werden nicht mehr benötigt:
  libevent-core-2.1-7 libevent-pthreads-2.1-7 libhtml-template-perl libmecab2 libprotobuf-lite23 mecab-ipadic mecab-ipadic-utf8 mecab-utils xul-ext-ubufox
Verwenden Sie »sudo apt autoremove«, um sie zu entfernen.
Die folgenden zusätzlichen Pakete werden installiert:
  accountwizard akonadi-backend-mysql akonadi-server kaddressbook kde-config-mailtransport kdepim-addons kdepim-runtime kdepim-themeeditors kf5-messagelib-data kio-ldap kio-sieve kmailtransport-akonadi ktnef
  libkf5akonadi-data libkf5akonadiagentbase5 libkf5akonadicalendar-data libkf5akonadicalendar5abi2 libkf5akonadicontact-data libkf5akonadicontact5abi1 libkf5akonadicore-bin libkf5akonadicore5abi2
  libkf5akonadimime-data libkf5akonadimime5 libkf5akonadinotes-data libkf5akonadinotes5 libkf5akonadiprivate5abi2 libkf5akonadisearch-bin libkf5akonadisearch-data libkf5akonadisearch-plugins
  libkf5akonadisearchcore5 libkf5akonadisearchdebug5 libkf5akonadisearchpim5 libkf5akonadisearchxapian5 libkf5akonadiwidgets5abi1 libkf5alarmcalendar-data libkf5alarmcalendar5abi2 libkf5calendarcore5abi2
  libkf5calendarsupport-data libkf5calendarsupport5abi1 libkf5calendarutils-bin libkf5calendarutils-data libkf5calendarutils5abi1 libkf5contacteditor5 libkf5dav-data libkf5dav5 libkf5eventviews-data
  libkf5eventviews5abi1 libkf5grantleetheme-data libkf5grantleetheme-plugins libkf5grantleetheme5 libkf5gravatar-data libkf5gravatar5abi2 libkf5identitymanagement-data libkf5identitymanagement5abi1
  libkf5imap-data libkf5imap5 libkf5incidenceeditor-bin libkf5incidenceeditor-data libkf5incidenceeditor5abi2 libkf5kmanagesieve5 libkf5kontactinterface-data libkf5kontactinterface5 libkf5ksieve-data
  libkf5ksieve5 libkf5ksieveui5 libkf5ldap-data libkf5ldap5abi1 libkf5libkdepim-data libkf5libkdepim-plugins libkf5libkdepim5abi2 libkf5mailcommon-plugins libkf5mailcommon5abi4 libkf5mailimporter-data
  libkf5mailimporter5abi1 libkf5mailimporterakonadi5 libkf5mailtransport-data libkf5mailtransport5abi2 libkf5mailtransportakonadi5 libkf5mbox5 libkf5messagecomposer5abi2 libkf5messagecore5abi2
  libkf5messagelist5abi1 libkf5messageviewer-plugins libkf5messageviewer5abi5 libkf5mimetreeparser5abi3 libkf5pimcommon-plugins libkf5pimcommon5abi3 libkf5pimcommonakonadi5 libkf5templateparser5abi2
  libkf5tnef-data libkf5tnef5 libkf5webengineviewer5abi3 libkgantt2 libkgantt2-l10n libkolabxml1v5 libkpimgapi-data libkpimgapicalendar5 libkpimgapicontacts5 libkpimgapicore5abi1 libkpimgapitasks5
  libkpimimportwizard5 libkpimitinerary-data libkpimitinerary5 libkpimpkpass5 libkpimsmtp5abi1 libmariadb3 libphonenumber8 libprotobuf23 libqt5keychain1 libqt5networkauth5 libqt5sql5-mysql
  libsasl2-modules-kdexoauth2 mariadb-client-core-10.6 mariadb-common mariadb-server-core-10.6 mbox-importer pim-data-exporter pim-sieve-editor
Vorgeschlagene Pakete:
  akonadi-backend-postgresql akonadi-backend-sqlite clamav spamassassin | bogofilter | spambayes | bsfilter | crm114 osmctools
Die folgenden Pakete werden ENTFERNT:
  mysql-client mysql-client-8.0 mysql-client-core-8.0 mysql-server mysql-server-8.0 mysql-server-core-8.0
Die folgenden NEUEN Pakete werden installiert:
  accountwizard akonadi-backend-mysql akonadi-server kaddressbook kde-config-mailtransport kdepim-addons kdepim-runtime kdepim-themeeditors kf5-messagelib-data kio-ldap kio-sieve kmail kmailtransport-akonadi
  ktnef libkf5akonadi-data libkf5akonadiagentbase5 libkf5akonadicalendar-data libkf5akonadicalendar5abi2 libkf5akonadicontact-data libkf5akonadicontact5abi1 libkf5akonadicore-bin libkf5akonadicore5abi2
  libkf5akonadimime-data libkf5akonadimime5 libkf5akonadinotes-data libkf5akonadinotes5 libkf5akonadiprivate5abi2 libkf5akonadisearch-bin libkf5akonadisearch-data libkf5akonadisearch-plugins
  libkf5akonadisearchcore5 libkf5akonadisearchdebug5 libkf5akonadisearchpim5 libkf5akonadisearchxapian5 libkf5akonadiwidgets5abi1 libkf5alarmcalendar-data libkf5alarmcalendar5abi2 libkf5calendarcore5abi2
  libkf5calendarsupport-data libkf5calendarsupport5abi1 libkf5calendarutils-bin libkf5calendarutils-data libkf5calendarutils5abi1 libkf5contacteditor5 libkf5dav-data libkf5dav5 libkf5eventviews-data
  libkf5eventviews5abi1 libkf5grantleetheme-data libkf5grantleetheme-plugins libkf5grantleetheme5 libkf5gravatar-data libkf5gravatar5abi2 libkf5identitymanagement-data libkf5identitymanagement5abi1
  libkf5imap-data libkf5imap5 libkf5incidenceeditor-bin libkf5incidenceeditor-data libkf5incidenceeditor5abi2 libkf5kmanagesieve5 libkf5kontactinterface-data libkf5kontactinterface5 libkf5ksieve-data
  libkf5ksieve5 libkf5ksieveui5 libkf5ldap-data libkf5ldap5abi1 libkf5libkdepim-data libkf5libkdepim-plugins libkf5libkdepim5abi2 libkf5mailcommon-plugins libkf5mailcommon5abi4 libkf5mailimporter-data
  libkf5mailimporter5abi1 libkf5mailimporterakonadi5 libkf5mailtransport-data libkf5mailtransport5abi2 libkf5mailtransportakonadi5 libkf5mbox5 libkf5messagecomposer5abi2 libkf5messagecore5abi2
  libkf5messagelist5abi1 libkf5messageviewer-plugins libkf5messageviewer5abi5 libkf5mimetreeparser5abi3 libkf5pimcommon-plugins libkf5pimcommon5abi3 libkf5pimcommonakonadi5 libkf5templateparser5abi2
  libkf5tnef-data libkf5tnef5 libkf5webengineviewer5abi3 libkgantt2 libkgantt2-l10n libkolabxml1v5 libkpimgapi-data libkpimgapicalendar5 libkpimgapicontacts5 libkpimgapicore5abi1 libkpimgapitasks5
  libkpimimportwizard5 libkpimitinerary-data libkpimitinerary5 libkpimpkpass5 libkpimsmtp5abi1 libmariadb3 libphonenumber8 libprotobuf23 libqt5keychain1 libqt5networkauth5 libqt5sql5-mysql
  libsasl2-modules-kdexoauth2 mariadb-client-core-10.6 mariadb-common mariadb-server-core-10.6 mbox-importer pim-data-exporter pim-sieve-editor
0 aktualisiert, 119 neu installiert, 6 zu entfernen und 48 nicht aktualisiert.
Es müssen 44,0 MB an Archiven heruntergeladen werden.
Nach dieser Operation werden 13,7 MB Plattenplatz zusätzlich benutzt.
Möchten Sie fortfahren? [J/n] J

After installation is finisched, acces to any user is gone.
Even the root user does not have any rights anymore!!!

root@kubuntu:~# mysql
ERROR 2002 (HY000): Can't connect to server on 'localhost' (115)