I’ve upgraded my website to Symfony 5.4 from 4.4. I’ve continued on without Symfony Flex, as I had when updating from 3.4 to 4.4. The procedure was fairly similar to that, fixing any Symfony 4 deprecations and then updating the composer version constraints, fixing anything broken after that. I also switched from requiring the symfony/symfony repo to requiring individual components. It went fairly smoothly, aside from needing to fix a few things after the composer update.
I’m kind of excited that we moved the first site onto a new server setup at Cogneato. I had worked off and on on the setup for months before we finally went forward with it. It brings a new OS, new host, new software, and a number of other changes to our previous setup.