If those packages are not compatible with newer Laravel versions by now then you should not depend on them since the maintenance is not guaranteed. I suggest instead of making pull requests to those packages you should fork them and maintain yourself. Cause if you create a PR who know if it will be accepted and even more when it will be merged. So do not waste your time waiting for people who do not plan to work on those packages frequently.
Maybe your best shot is to see if there are any updated forks of those packages. Hope you have tests to make sure those replacements do not break anything.
Problem is also that you do not know if there are any dependencies of those problematic packages that also need to be updated. This is the exact reason why I try to not depend on packages as much as possible and develop my app as a package so I can quickly upgrade.