I was writing an answer to a GitHub user that wanted to contribute to Plone/collective and I wrote this:
Basically, find an add-on of your liking and do the 3 minimal conversion steps:
move to src layout
apply plone.meta
convert to Python native namespace (PEP 420)
With these steps, it will be highly likely that your add-on is fully compatible with Plone 6.2, specially as the 3rd step is needed, and to get there, doing the other first two (in that order) makes the whole process easier.
If you look at any plone repository, say plone.batching, you will find PRs for each of those steps, and on docs.plone.org there is documentation on how to apply them (not for src layout, though, but you can look at the PR commits of any plone repository converted to a src layout).
We should maybe make a list of add-ons and check how many are converted and see how we improved until the Plone Conference
