It will likely come with the next patch release, which is planned for next Monday/Tuesday.
(For 2.4)
Exact same issue for me..
I ran an even older version though, and upgraded to Trixie, to find some time later the graphs/trending/history data was missing. 
Decided to upgrade checkmk to 2.4.0p15 to find the issue is not yet fixed. Looking forward for this update.
We will then wait for the release next week before evaluating any further.
Coming officially now with 2.4.0p16.
Planned for Monday/Tuesday
What about checkmk 2.3?
I cannot use checkmk (raw) 2.4 due to the significantly higher memory consumption.
CheckMK 2.4.0p16 has Debian 13 support, and it works well, thanks.
You can find our list of supported systems for Checkmk 2.3 here: System requirements
We do not plan to backport Debian 13 support to Checkmk 2.3. 2.3 already supports 3 major Debian releases and the cost for maintaining, building, and testing such a big zoo (14 supported distributions) is already too high.
This is great news, thanks! 
Is there any reason why the git tags are missing for everything after v2.4.0p12 at Tags ¡ Checkmk/checkmk ¡ GitHub?
No idea, but we donât really use that ourselves.
Would be great if the tags could be pushed again (being able to fetch the tar.gz is relevant for some folks :)), thanks for consideration
I updated yesterday , and for me the graph data is back again. Hurray
If you are already on CheckMK 2.4.0p16 on Debian 12, make sure to install the Trixie package of CheckMK 2.4.0p16 again after doing the Debian upgrade.
In my case it was needed, otherwiese CMK wonât start (but I may missed this step in the upgrade guide 
)
After that it works fine for me as well (CheckMK 2.4.0p16 on Debian 13.2)
Thx for support 
for all who will upgrade debian. there is an dependency to libevent-2.1-7 which is obsolete now.
This package will not updated when installing p16 on debian 13. You should install libevent-2.1-7t64 which replaces libevent-2.1-7 to have an cleaner os