Wow...sorry but so much bad advice here. First don't upgrade in place as a best practice due to carrying over old versions of software...rather create a new fresh server and deploy and test there. Second, the upgrade wizard hasn't been supported for years since 2016 unless you're upgrading an earlier version than that. Why are people still saying to use it is beyond me (it'll just show list of no packages to upgrade - have fun with that). Third, upgrading takes place in VS/SSDT and happens twice, once when you change deployment to 2019 version and then when you open every package. And every package you open takes a millenium to open. So far I've found no workaround for that.
There is an upgrade SSISDB wizard - I wouldn't do that because again you're upgrading existing rather than starting new which inherits any legacy debt on your server.