Unless you absolutely need it, I would stay far away from Adobe Flash . It runs on Chrome I believe although sandboxed, but in Firefox if you need to use flash you will need to have it in your system. There are just too many vulnerabilities day after day , another exploit in flash. Flash is going by the way of horse and wagon it’s just a matter of time.
I do understand that some people need to use it for work purposes, but if you really could get away with HTML5 then use that…that is until they find a way to compromise that too…:\
You can do it via Yast -software management. Search for flash. look at the version tab at bottom right. deselect the version from adobe and select the the one from openSUSE
Then in Yast repository management remove the Adobe repo