First: huge thanks to @thatswinnie and @PhilippeLM . Winnie for pointing me to Philippe and Philippe for pointing me to the right forum-entries and his helpful posts to get it to work in Linux with 1Password 4 and Firefox. Supposedly it works with the Chrome-extension, too.
Please take note that this solution is not officially supported by AgileBits and can probably break with any update. But let’s hope that it doesn’t.
So 1Password is a pretty popular password-manager for OS X and there is also a version available for Windows. In addition there are great companion apps for iOS and Android1. Since I have licenses for all the versions, I wanted to continue to use it on Linux. But how?
First you have to install Wine. There should be a package for it in the package manager of your distribtion. Then start Wine once, so it can configure itself.
Next up, download 1Password for Windows and open the downloaded exe. It should be opened by Wine and start the installer. Just let it do its thing. Then you have to edit the following file ~/.wine/user.reg2 for disabling browser validation.
Search for [Software\AgileBits\1Password 4] and add beneath it a new entry:
Save the file, open 1Password and restart the 1Password Helper. This option is in 1Password in Help – Restart 1Password Helper.
Then you have to download and install the Browser-Add On/extension from AgileBits. Restart your browser and it should work. I had to restart the 1Password Helper once more and after that it worked flawlessly for me.
Update: I have now my real machine and couldn’t get it to work even with this manual. To get the 1Password-extension working I had to open the preferences of 1Password, had to go to the Browsers-tab and check „Unlock on Secure Desktop“. After a restart of Firefox, it worked.