I bet you can get plenty of support for MySQL or Postgres
There is no vendor so you're relying on third parties many of whom are mom and pop shops. And if you're a global, multi-national well good luck finding someone who you can cut a deal with for global support. Not to mention that the support is hardly likely to be top tier.
You're generally either dealing with EnterpriseDB, or you're dealing with a company that is run by people who are significant contributors to the project — literally, on the core committee — or have people who have created meaningful parts of the PostgreSQL ecosystem.
You need to drop this FUD.
I will never again use or support an Oracle product after they literally, specifically cost a former employer $.75mm, on Cyber Monday by giving us factually false information.
Did your employer attempt to recover the money from Oracle? If not, did they even consider doing so?
EnterpriseDB has according to LinkedIn between 200-500 people mostly located in AMR and EMEA based on experience with their APAC division. They simply are NOT a top tier support company on par with Oracle, Teradata, SAP etc. I am based in APAC and so my opinion is going to be far different than other parts of the globe.
And the difference with DataStax, MongoDB etc is that those companies are basically the open source projects. They control the steering committees, copyrights, branding etc. And so there there's a lot more confidence in being able to reach someone who actually wrote that part of the code. PostgreSQL has always been far more decentralised.
AWS.
While multi-master replication is still not there (it's still just a synchronous standby and read slaves) all of the heavy lifting is done for you.