https://tahti.studio/
sample sequencer inspired by elektron, allows you to share your projects via a link, so submissions can be similar to jummbox, in that there's a link.

is there an offline version which allows you to open projects even if the website itself dies?
this is the case for jummbox which is the only reason why it can be a format here.

no, maybe in the future

yar, i think it only makes sense to discuss this as a potential format as soon as archiving the tool and projects entirely, unconnected from the current website

also on the website it says that the share links are temporal, which is a deal breaker :(

or perhaps a libre fork/alternative appearing in some git account around, who knows... :|