Quote from @Kaiden Foster:
It seems the general consensus is that it is nearly impossible to get liability insurance as a STR manager? What are STR management companies using then?
I talked to a lot of management companies to try and figure this out, and get contacts from them. I found two repeat things.
1) Insurers that used to offer on STR, but no longer do
2) Insurers that offer on "property management" which does not include STR, but the people buying the policy didn't notice.
#2 is the scary one. I had probably 10 people refer me to Hiscox. The first 2 agents at Hiscox were happy to sell me "property management" insurance even after I explained to them explicitly what I did (short term rentals only). It wasn't until the 3rd agent finalizing things that they said the policy does not cover STR, and that they do have a policy that covers STR.
Ultimately your best bet is going to be to find a local company. Most of the national ones won't do it. Someone in the same zip code as your property. Those still exist. Obviously this will be a pain if you operate in multiple markets, but it is what it is.