Can confirm the bit about dpkg options:
root@rpi4:~# cat /etc/apt/apt.conf.d/97dietpi | grep confold
DPkg::options:: "--force-confdef,confold";
I have already manually fixed it, but in the projets github repo I have seen no source of that line of code, so I’m still wondering where it came from in the initial installation.
Anyway, my problem is temporarily fixed, and I know how to fix it next time.
Thanks everybody!