Details at https://twtxt.dev/ and elsewhere. This has been in development since 2016. All you do is create a txt file in www or html and include info like

# nick        = username
# url         = https://example.com/posts.txt
# avatar      = https://example.com/avatar.png
# description = Describe this

to then begin posting using a command like like

echo -e "$(date -u +'%Y-%m-%dT%H:%M:%SZ')\tHello to all of you out there! >> posts.txt

There are various registries and places you can submit your user via curl to become more discoverable by others. Also tons of spin-offs that add support for fancier markdown and such, but haven't tried those yet.

Created a basic user and love the idea!

My mind went to fault finding and I think that a txt file that needs to be read as a whole each time could be a problem. Or is there something like delta downloads for simple files?

Then in realized that a single JavaScript include on sites like twitter would be ten times bigger than the average feed on twtxt.