@rugyada has provided us with some great tips here. Thanks @rugyada.
Post-edit: If I search with ‘Find’ “Transaction Summary” it will find all entries that say that starting with the very first one on Feb. 04, which is for 2280 packages, in other words the install. Then to the right of ‘Find’ there is a down arrow that take you to the most recent “Transaction Summary” from today. Something similar should be in everyone’s dnf.log.
Post-edit-2: Really good suggestions from @rugyada.
The .xz file below is the dnf.log I have been using as an example so it contains everything I have talked about above and lots more. If interested see if you can find the things talked about.
dnf.log.tar.xz (319.8 KB)
and if @Giorgio or anyone wishes to they can compare my file to yours and maybe we all learn some things.
And don’t anyone go thinking I’m smarter than any other users here or that I think that way. I am wrong sometimes and get to “eat humble pie”. I don’t think I will turn out to be wrong on this one but well you just never know until you know.
I use very often “Find” to search and I know I’ve to keep pressing key to go further.
I used “Find” to search for package names or other significant words but i don’t find anything corresponding to updated packages.
Then I think my dnf.log is probably different from yours. Not a big problem for me, now I’ve an easy alternative to list updated packages.
First post your entire dnf.log as a file here and we can see if this is true.
Another exercise, simply do this:
Open ‘/var/log/dnf.log’ with Kate. Select ‘Edit>Find’ and type in the ‘Find’ bar “Transaction Summary”
and it should look like this:
Post-edit: Won’t matter if user is updating with dnfdragora (strongly not recommended) or command line (strongly recommended) everyone should have this in their dnf.log because this is showing the original installation of your system for Calamares.
@rugyada can you check and confirm whether dnfdragora is logging dnf transactions, here it looks like it is not. If so that is absolutely horrible.
Post-edit: And I’m all but certain that I’m about to get another opportunity to admit I was wrong about some things above. Not all of it but some of it.
So I asked Son_Goku on IRC (he is one of the principle authors of dnf and dnfdragora) and dnfdragora transactions are definitely supposed to be logged in the dnf logs. But my own investigation shows that they aren’t currently. Indicating I was right that the information is supposed to be there but that @Giorgio was right in insisting that his logs are different. And the possibility that his logs might be different because of bug with dnfdragora did not occur to me until today.
It would be strongly advised to not use dnfdragora until this issue is addressed. Discussion here.
dnfdragor is not logging transactions in logs.
https://issues.openmandriva.org/show_bug.cgi?id=2454
The answer to the original question in this thread and to it’s title is provided by @rugyada thus:
$ rpm -qa --last
So let’s close this thread and deal with the issues with dnfdragora and dnf logs here.
I made an effort 
and installed using dnfragora
Checked and confirmed.
Nothing in log files dnf.log, dnf.rpm.log or hawkey.log
