For the record; we consider the new authority on the Twtxt spec(s) going forward (has been for some years actually) to be implementers / primary maintainers of widely used clients. To date that is:
yarnd
@prologic@twtxt.net (me and others)
jenny
@movq@www.uninformativ.de
tt
@lyse@lyse.isobeef.org
Timeline
@darch@neotxt.dk / @eapl.me@eapl.me and others
twtxt-el
? – @andros@twtxt.andros.dev
Full list of supported and widely used clients can be found at https://twtxt.dev/clients.html – which I note a few above are actually missing from this page haha 🤣