@NeonPurpleStar @elCelio seats are roughly proportional to the vote share, but d'hondt arithmetics are slightly biased to favor bigger parties
in 2008 BZÖ and FPÖ got 55 seats combined. FPÖ now has 57. you could argue that being divided cost both parties a single seat each
to form a government only two rules are in play (always!):
1) the president (former green party leader van der bellen) can pick basically anyone to form a goverment
2) a >50% majority in parliament can fire the government