@Gregor B. welcome to BP and best of luck on your journey! I'm based in the UK but have done property in the US and UK. It's great that you are seeking out accountant references. I have been astounded how much tax can matter, even if I haven't wanted to be tax led. Having studied investments I always wanted to let the investment proposition lead and tax follow but tax can wipe out much of your gains, or on the flip side there can be big tax advantages.
If you are mobile within Europe you may want to research Portugal's program where your non Portuguese sourced income is not taxed there. I am not sure how that works for EU citizens--I have been learning about the Portugal option from US citizens who have achieved FIRE (financial independence retire early). It sounds like there is a blossoming expat community in Lisbon, some of whom also have real estate investments in the USA.
If you're tied to Austria maybe google the FIRE movement there in case there are meet ups. I have been pleasantly surprised that even in fairly high cost London there is a FIRE movement. The reason I mention all these meet ups is it might be a way to meet people who have a similar situation to you (onshore EU investing in USA)