If using a SeedSigner for a multisig, it’s still good practice to not put more than one of the seeds through the same device. If you really want to minimize your attack vectors, I think it’s still a good idea to use hardware wallets as well so that it is multi vendor. Also, hardware wallets store a backup of your multisig configuration as well.

The SeedSigner does have some additional vulnerabilities; i.e. you need to verify the software before downloading it. If you really want to be paranoid about it, you should never leave the device anywhere that anyone could access it, bc someone could tamper with the hardware, or even the software on the SD card. So you should keep it locked up, or verify the software on the SD card before using it, or use a fresh verified download each time, and examine the device for tampering. These are high paranoia concerns though. Also, I’m not an expert lol. Definitely steel backups for all seeds though.