Why can’t I use ,,pravidelně”? I see this used much more often than the other adverbs.
In this case, pravidelně would mean 'regularly' as in 'occurring at fixed or prearranged intervals'
Perhaps you confused that with zpravidla which can be used here as a synonym for obvykle.
Obvykle is the most common, I'd say.
Why is "Obvykle jezdím sem autem” wrong?
Sem is an inconstant clitic, it wants to be in the second position when it is not stressed.
And where is this explained in Duolingo?