> This was true mostly all the way up until the bachelor reforms in the 2000s. Nowadays, there are quite a lot of classes that you have to sit in (depends a lot on the university and courses)
It varies a lot. In our university in the 2010s, nearly no computer science course had attendance requirements, but it was somewhat common in business administration (maybe one third of courses with mandatory attendance)
In one of my CS/math courses, the professor told us that he never went to class when he was an undergrad, so he didn't expect us to, but it would probably be a worthwhile trek from your bedroom.
With the reforms since then, I think the general modus operandi now is that lectures do not require attendance, however almost every course has tutorials with attendance and weekly assignments. If or how this is enforced is completely up to the professor though, and some do not care.
> however almost every course has tutorials with attendance and weekly assignments
I don't think this is true for the vast majority of majors. Admittedly, in the natural sciences it tends to be more common to have weekly assignments but whether they are mandatory (or can be made so) or not depends on the university and has also been the subject of legal disputes. Mandatory attendance of tutorials, however? I've only ever heard that of medicine but those guys are crazy, anyway. (They basically saw your skull open and try to stuff as much in there in as little time as possible until you puke it out again during your exam. Not sure that's an effective method to learn…)
It varies a lot. In our university in the 2010s, nearly no computer science course had attendance requirements, but it was somewhat common in business administration (maybe one third of courses with mandatory attendance)