I am looking for a wallet I can keep in cold storage (an offline machine) which can occasionally sign txes and have a hot wallet send them. I’m having trouble finding a wallet that supports this. Or is multisig a better way to do this?
Preferably OSS, preferably run on Linux, needs a GUI.
Would a hardware wallet suffice? Or does that not meet your requirement of needing a GUI?
Otherwise what about running Electrum on an old laptop with the network card removed?
In any case the hot wallet could be a watch only wallet under Electrum. Whatever you choose for the cold wallet, you could sign transactions there and broadcast them from the hot wallet.