Raise to Answer would only work if there is a proximity sensor, which perhaps some feature phone might have, but a flip phone probably won’t, and it can be set to answer when opening the flip, so that’s fine.
Regarding Catima, I shall answer here because it works but it has some issues which are common with other apps when used on flip phones:
The save icon seems to be floating over the contents in the lower right corner. (This is also true of the search icon for the f-droid app.) I can usually get it to work, but it would behave ‘better’ if it were in the regular flow of objects. I can get to the save icon in the ‘card’ tab, but not while in the ‘photos’ tab. The delete icon is easy to get to, so perhaps it could be next to that.
When adding a card, the options allow the entry of notes. This field captures the cursor. The right key adds a space, and the down key starts a new line, but nothing allows me to move to the next field below the notes. I can use the up key to escape to the top, but I cannot get to anything below the notes field. I have seen this in other apps as well.
The third-party mouse probably would make these issues go away, but it requires some work to install. I did request the manufacturer of my particular phone add an app cursor, and they actually replied, saying that it sounds like a good idea for a future release. I’m sure there are other phones without an app cursor, so hopefully it will be easy to adjust the apps slightly.
(And Catima seems like a very practical app for many people.)