For support of RHEL 8, you need to have at least ITM 6.3 FP7 SP2:
https://www.ibm.com/support/pages/ibm-tivoli-monitoring-630-fix-pack-7-service-pack-2-6307-tiv-itm-sp0002-readme
SP10 is currently the latest one:
https://www.ibm.com/support/fixcentral/swg/doSelectFixes?options.selectedFixes=6.3.0.7-TIV-ITM-SP0010&continue=1
#Support#SupportMigration#Tivoli