Has the Swedish government determined that flying the Daesh flag is
not hate speech?
They determined that a long time ago. According to current Swedish laws, someone waving the black standard used by Daesh can not be prosecuted or arrested by Swedish security forces. The Independent reports:
Flying the Isis flag in Sweden is not illegal and cannot be considered
an incitement to racial hatred, according to a Swedish prosecutor.
A 23-year-old man from Laholm has avoided prosecution after he
allegedly posted a picture of himself with the Isis flag as his
Facebook profile photo.
The black standard is not exclusively a symbol of Daesh. Other organizations use it too. As far as I know, there are at least three organizations that use it:
1. Al Shabab

2. Al-Qaeda in the Arabian Peninsula

3. Jund al-Aqsa

The Independent writes in another article:
Is the flag unique to Isis?
Monochrome flags are an ancient tradition in ancient Eastern, Arabic,
and Islamic tradition, and some people believe one of the Prophet’s
original banners was black, according to the Quilliam Foundation.
Modern jihadists therefore adopted this style to legitimise their
causes.
Therefore, the flag is in fact not unique to the group, according to
Charlie Winter, senior researcher on Jihadism at the counter-extremism
think tank the Quilliam Foundation.
“A lot of people talk about the Isis flag or the Islamic State flag,
however there is no such thing. It’s a flag they have adopted that has
political and theological significance.” he told The Independent.