The application should have no trackers, it must be open source (or FOSS) and very complete in functions, not too basic.
If there is something else, you can add to the list and make it more complete. There is “something else” option for that.
No need to use what is installed by default on /e/, however, if you find that the specific /e/ application is so good and should be mentioned, you can put it in the list as well, but if you consider there is something even better, you can also put in, it’s up to you.
I haven’t done my list yet because I’m still searching for good options, so can’t say what is the best without having enough knowledge testing different options.