Custom widgets cannot be used in Experience Builder until Enterprise v11.0. But my organisation still uses Enterprise v10.9.1 with no upgrade in the pipeline.
However, both implementations share the same version of Node.js (v14). While JSAPI has changed, we can easily reference the updated version. See Version History
With these things considered, can an app (and associated custom widgets) developed in the newer version be run on an older Enterprise Portal?
If no, can any manual (re)configuration enable this? Are there any creative workarounds?
What about Experience Builder Developer? We've been able to use it to take advantage of new capabilities as soon as they are available, rather than wait for it to hit Enterprise.