On-premises support is in progress. No release date yet. That said, would you need it to be fully self-hosted or would it be viable to have an on-premises agent?
Relay uses Tekton under the hood to run workflows and Knative to process triggers. What kinds of workflows are you thinking about running?
Fully self hosted is a requirement in my case. Letting an agent that's essentially externally controlled would be a hard sell in corporate environment.
In my case, I need very simple workflows that e.g. run Ansible playbooks, or do non-urgent monitoring, bookkeeping, and essentially trigger scripts. I usually need a single step - no serious need for a pipeline/workflow even. Cron job and manual triggering would be enough to cover the base usage (though git hook would be next on the list).
The more "convoluted" part that I'd want to see is a capability of jobs controlling themselves (e.g. job disabling itself or others on error), jobs as code, flexible notification system, and make it easy to deschedule/disable jobs in bulk, easy to extend with plugins.
Granted, Rundeck has most of what I need, but the implementation is Java, which also includes its SSH functionality.
Relay uses Tekton under the hood to run workflows and Knative to process triggers. What kinds of workflows are you thinking about running?