Every release typically offers direct upgrade paths from at least the previous one or two releases. You can upgrade directly to 2021 R1 from 2020 R1 (20.1.x.x) including:

To upgrade from a release that is earlier than 2020 R1, you must perform multiple upgrades, one for each major release. For help with upgrading from a release that is earlier than 2020 R1, please contact aPriori Customer Support or Professional Services.