I'm finding dead ends in my searches. First tried Hub Link but when I tried to load Bravenel's Send Hub code I get an error message. Tried the links for Hub Connect and they were broken.
I'm moving from ST and would like to link the hubs if that is still possible.
It's worth mentioning that SmartThings can remove their Groovy IDE based interface at any moment as they have been preparing for Groovy demise for a while now. Hub Connect also uses legacy SmartThings Groovy, as far as I know.
Where are you installing this code? That is SmartThings code, and there is nothing you need to install on Hubitat for Hub Link/Send Hub Events.
Along these lines, beyond the fact that ST will eventually (soon?) discontinue their classic Groovy IDE and thus both HubConnect and Send Hub Events will no longer work as-is, it should be noted that the latter is one-way: ST events to Hubitat. It doesn't "sync" devices in the other direction, just in case this matters for your use. Some people thus prefer HubConnect.
Node-Red with the Samsung Automation Studio pallet uses the new Smartthings API. If you need long term support this will be your best option. It takes a little to setup though.
The things your need just for polling Smartthings are:
A always on computer to run Node-Red. This can even be a Raspberry pi.
To load the hubitat pallet and Samsung Automation Studio Pallet into Node-Red
A Samsung developer token for your Smartthings account.
If you need Smartthings to send immediate event changes you will also have some additional work