Mirth is the commercial offering many people use - it is nice because it handles the MLLP protocol, gives you a mapping system, lets you transform and call your own endpoints. That’s also why it sucks: it’s a big heavy system.
It might not be great but I think its better then most offerings.
IMHO Redox is now so expensive that you have to wonder if you might be better off doing all of this work yourself. As others have mentioned, there is a free Mirth offering and parsing HL7v2 is not that bad.
But I already have thousands of independent VPN setups and API integrations, so the cost is harder to justify at scale.