I'm looking at purchasing support for our MariaDB database from a number of providers including MariaDB, Percona, MinervaDB, and DatAvail. How do I go about determining how good their support is? I've not managed to find any forums that discuss the paid support offerings from these companies, and I know I can ask them for customer references, but I'm wary of the selection bias you get with that approach. My experience with paid support is that it can range from "for $$$/yr they're less helpful than google" to "they saved us months of struggle". Do you have any experience with support from any of these companies? Any other suggestions on how to go about gathering info on them?

Thanks,
-Eric