txt file is great. Makes me wonder, does the author always have their laptop on them since that's the only place I know of where a txt file can live? Do they go to sleep and wake up next to their laptop?
I've always been an iPhone user and have never seen a .txt file on one and probably you wouldn't be able to edit one on an iPhone if you did have it in Files app - I'm not counting Notes app as a text file here.
I do quarterly notes inside of Notes app but it mostly non-work related stuff and doesn't integrate well with desktop since its kind of a pain to login to iCloud from browser. Quarterly notes bc once the note gets too long, it gets very laggy on phone and is difficult to navigate; i.e. getting to the bottom to write a new line can be tough on mobile.