akonadi problem in full-upgrade deb 10 upto deb 11

Hi,
I tried to upgrade current stable debian 10 to testing debian 11 on two machines and got the same problem on both: akonadi server stopped starting.

Application: akonadiserver (akonadiserver), signal: Aborted

[KCrash Handler]
#4 0x00007f259de25ce1 in raise () from /lib/x86_64-linux-gnu/libc.so.6
#5 0x00007f259de0f537 in abort () from /lib/x86_64-linux-gnu/libc.so.6
#6 0x00007f259e227bf1 in QMessageLogger::fatal(char const*, ...) const () from /lib/x86_64-linux-gnu/libQt5Core.so.5
#7 0x0000563d82e67ad4 in ?? ()
#8 0x0000563d82f99673 in ?? ()
#9 0x0000563d82e67d0f in ?? ()
#10 0x00007f259de10d0a in __libc_start_main () from /lib/x86_64-linux-gnu/libc.so.6
#11 0x0000563d82e6a8ca in ?? ()
[Inferior 1 (process 66635) detached]

default: Connecting to deprecated signal QDBusConnectionInterface::serviceOwnerChanged(QString,QString,QString)
2021-05-19T15:36:21 [WARN ] org.kde.pim.akonadicontrol: ProcessControl: Application '/usr/bin/akonadiserver' returned with exit code 253

I searched the web with no results for me ...

Many thanks in advance for any advice

WBR,
Andrei