I think you might have a firewall. First try using 127.0.0.1 instead of 192.168.4.116
in /electrs/config.tomlelectrum_rpc_addr = "127.0.0.1:50001"
hah! my electrum_rpc_addr was
already set to 127.0.0.1, changing it back to the local IP 192.168.4.116 has (so far, I think, still indexing) resolved the address lookup issue!
~$ curl -sSL "
http://mempool.myserver/api/address/1KXLMMcwtB9VsbBXboaV6AxUv7mmomWEeR"
{"address":"1KXLMMcwtB9VsbBXboaV6AxUv7mmomWEeR","chain_stats":{"funded_txo_count":0,"funded_txo_sum":979079,"spent_txo_count":0,"spent_txo_sum":0,"tx_count":1},"mempool_stats":{"funded_txo_count":0,"funded_txo_sum":0,"spent_txo_count":0,"spent_txo_sum":0,"tx_count":0},"electrum":true}
However, this does mean that I can no longer connect my desktop electrum to the hosted instance via the onion address which was working before (when I had rpc_addr set to 127.0.0.1) but this is a minor issue, I can probably resolve w opening the port through NAT.