With the recent release of BMC Discovery On-Premise 20.02 (12.0), now would be a great time to review:
1) What version of BMC On-Premise Discovery you are currently running:
2) What the supportability timeline looks like for that version. The page in the link below contains information about the support lifecycle dates for BMC On-Premise Discovery.
3) Your plan is to upgrade/migrate to a newer version of BMC On-Premise Discovery:
4) End of vendor support for CentOS 6.
The above should be a good starting point for determining what your timeline should be for an upgrade or migration to the latest version of On-Premise Discovery.