Thank you for the hint, great work at Dietpi!
I certainly tried beforehand to “check for the already existing similar topics”.
I think I now found the answer in
https://github.com/MichaIng/DietPi/issues/7544#issuecomment-3218033235:
“However, in case of HA, so far while there is no end user support for 32-bit setups anymore, it still works. It may break any time, but so far Python has been sort of resilient, even for armv6l, making https://piwheels.org/ possible.”
→ agree, «32-bit is dead"», and more and more packages will become unsupported. Yet for my use case this little machine suits well, currently no need to have larger setup running 24/7.
So I hope Dietpi maintains support of armhf for still a little while. And I am preparing a docker instance, as backup just in case …