First of all, can you please remove the chainconfig, with v10 you can configure everything on the dashboard.
Secondly, you can “partake” everything that we have on sapphire_mainnet, on sapphire_devnet as well. Its just that it is meant for production use with servers that scale up based on the demand of our clients.
You can try out all the features gated on sapphire_mainnet for FREE on sapphire_devnet projects, it is not limiting in any regard.
I hope this makes sense.
And I tried out the your sample app, it works well without any issues for me: Jam