Welcome to LQ.
If you really want to stick with Quicken, you have three alternatives.
Run it under wine. It seems to do from pretty good to okay in that way. Wine is likely in the repos for your distro, if you are using a distro with repos:
Run in a virtual machine, using VirtualBox or some similar program (most distros I've tried have VirtualBox in the repos):
Keep a Windows box for running that one app.
There is Gnucash, which is a native Linux app, but I've never used it. My finances are much simpler than I would like them to be: