在多条链上调用处理程序

I am not sure about all chains because it really depends on whether or not the RPC provider that the Upgrade Indexer is using supports them. What were the specific chains that you were after? Arbitrum in particular, but if a subgraph that uses call handlers can't be reliably used on all networks then I'm not sure call handlers can be used for multi-chain projects. Seems like a pretty big limitation on this feature.