why do free AV's think it's ok to push popups?
In short.
Because the use it to promote their pays products.
They are after all commercial companies and have to make money if they want to keep existing.
So the install tries to put bloat on your PC as default (lots of features you don't need), so selecting minimal installation solved that problem
What is needed/wanted is all for the user to decide.
You might things not needed while others are sure they need them.
How do they say that...
Beauty is in the eye of the beholder ?
The settings UI is still complicated and over-done (I've seen worse, Avira for example) but 5 minutes should be enough to find the privacy option to stop sending data to Avast
Took me about a minute to find it.
But as with all software, you need to spend time learning how to use it.
What settings it is offering the user, what the settings do etc.
And as often is the case, it is also a matter of getting used to things.
Complicated ?
That depends on the user.
What knowledge the user has, capability of logical thinking etc.
Some find it complicated, others find it real easy.
The problem is that the UI is always a compromise.
Put only a few options in it and people start complaining that they can't find/change certain settings.
Put many options in it and people start complaining it has to many options.
You could say the UI is based on what the average users would like to see.
So why am I uninstalling Avast this time round? Windows did not find antivirus software on this computer
Let me guess, you are using Windows Vista.
If you do, a little (re)search would have told you the problem is know and that avast is already working on it.
As for trying multiple av's, I sure hope you removed everyone completely before install a new one.
If not you will have a lot of trash on your system and it can lead to problems.
https://blog.kaspersky.com/multiple-antivirus-programs-bad-idea/2670/Removing through control panel and/or using the removal tool from a vendor is not removing everything.
Only way to do so it to remove it manually.