At my system, this is the journal log when filtering for those kernel messages:
oliver@freedombox:~$ sudo journalctl -q -g "Linux version"
Failed to get MESSAGE field: Bad message
Jul 13 17:29:26 freedombox kernel: Linux version 5.10.0-8-armmp-lpae (debian-kernel@lists.debian.org) (gcc-10 (Debian 10.2.>
Jul 13 17:29:26 freedombox kernel: Linux version 5.10.0-8-armmp-lpae (debian-kernel@lists.debian.org) (gcc-10 (Debian 10.2.>
Jul 13 17:29:26 freedombox kernel: Linux version 5.10.0-8-armmp-lpae (debian-kernel@lists.debian.org) (gcc-10 (Debian 10.2.>
Jul 13 17:29:26 freedombox kernel: Linux version 5.10.0-8-armmp-lpae (debian-kernel@lists.debian.org) (gcc-10 (Debian 10.2.>
Jul 13 17:29:26 freedombox kernel: Linux version 5.10.0-8-armmp-lpae (debian-kernel@lists.debian.org) (gcc-10 (Debian 10.2.>
Jul 13 17:29:26 freedombox kernel: Linux version 5.10.0-8-armmp-lpae (debian-kernel@lists.debian.org) (gcc-10 (Debian 10.2.>
Jul 13 17:29:26 freedombox kernel: Linux version 5.10.0-8-armmp-lpae (debian-kernel@lists.debian.org) (gcc-10 (Debian 10.2.>
Aug 18 02:00:52 freedombox kernel: Linux version 5.10.0-8-armmp-lpae (debian-kernel@lists.debian.org) (gcc-10 (Debian 10.2.>
Aug 18 09:19:41 freedombox kernel: Linux version 5.10.0-8-armmp-lpae (debian-kernel@lists.debian.org) (gcc-10 (Debian 10.2.>
As @sunil pointed out above, the identical time entries may stem from System clock time unset or jumped backwards, because there is no battery backed RTC clock.
There are no messages saying Linux version ... anymore after Dist-Upgrade to Bullseye, or so it seems. How is that?