I still do have the mSIGNA wallet. It doesn't offer any option to export single private keys. The only private key export option is said BIP32 extended private key.
The problem with the software is, I wasn't able to get it to connect to a node so far.
The .pdf I linked to above says it should connect to your own node. Are you running a node?
Can you import your seed phrase back in to mSIGNA and regenerate the same wallet with the same addresses? If so, then it is hopefully just a case of finding the right derivation path. But I worry given what is written on that .pdf it is going to be significantly more complicated since it apparently uses an unknown multi-sig arrangement.
I may not have made that clear in OP: But I can still access my wallet in mSIGNA. That's not the issue. This is where I got all the public keys and see a few of change funds still on there.
The issue is using the exportable keys as described in OP via 1), 2) or 3) to import properly via an other wallet.
Also, my wallet is NOT setup as a multisig, just a regular HD wallet. Multisig apparantly was optional.
My guess it's only about finding the right derivation path. Wonder if there is any tool to determine which is used by mSIGNA here.
Thanks for digging up that old pdf - no info on their derivation path used, though.
Seems the derivation path issue was already around in 2017:
https://bitcointalk.org/index.php?topic=2144498.msg21524209#msg21524209