any problems adding to hubitats to home assistant?
sorry I mean Two (2) hubitats
Just use HADB
That depends on what the OP wants to do.
HADB brings HA devices into Hubitat.
If OP wants to bring Hubitat devices into HA, that is different.
If you want to bring Hubitat devices from your 2 hubs into HA, you can do it several different ways.
You can share devices between the hubs via hub mesh and then bring them into HA via Maker API on the hub with all the deices you want to share to HA and the Hubitat integration in HA.
The other way is to run an instance of Maker API on each Hubitat hub, and then configure the Hubitat integration in HA with the info from each Hubitat hub.
If you want to bring your HA devices into Hubitat, then @rlithgow1 is correct and you need to use HADB.
@jack9jensen the Maker API integration requires this integration installed on Home Assistant via HACS: GitHub - jason0x43/hacs-hubitat: A Hubitat integration for Home Assistant · GitHub
An alternative would be to use MQTT: MQTT - Home Assistant
The newest alternative is HubConnect.
If you’ve never used HubConnect, the guide points to that how-to and after that detour, you install HubConnect for HA on your Home Automation system.
I took a fully reset Hubitat hub, downloaded the two HubConnect bundles, installed HubConnect and then added a Connect a Hub. I filled out the form, pasted the connection key to my freshly built HomeAssistant VM. Then completed the Hubitat Verify step. Done.
Although I do have plenty of experience with these Packages, it took under 5 minutes to do.
A couple minutes later I had selected a Hubitat device and mirrored it to HA.
This test was created to verify the instructions, not get something production ready. I have that running on my other Hubitat Hub and other HomeAssistant VM 
What are the advantages of HubConnect over the native Maker API? I have a handful of devices that have Home Assistant integrations available and not HE, that along with wanting nicer Dashboards has triggered me to set up a new HAOS PC and now am starting to work my way into tying into my HEs (I have an 8 Pro primary and a 5 in my shop as a secondary, but have a and 8 non-pro, that I need to swap out with the 5). I’m generally of the opinion that “less is more”, so not inclined to add more custom code than necessary. Is HubConnect any better/different than the native Maker API?
If you want something lightweight, I would also recommend considering the built-in MQTT integration that @bobbyD pointed out. That doesn't require the HACS hubitat integration at the HA end. Just standard MQTT.
The topic title is: Add hubitat to HA (paraphrased) and in that direction it’s pretty easy because device attributes on Hubitat can easily “fan-out” to entities on the HA end. It’s really the other direction, HA entities “fanning-in” to a single Hubitat device with one or more related attributes, that is complex. HubConnect already has all the data points to inform that decision, I think.
But yes, I agree with @aaiyar and @bobbyD that MQTT is going to be very light weight, but you get a device per entity, I believe.