offline web code apps allready portable?

i hope for a tip, as need very bad to find a solution on that to finally get life (again) managed, thx!
found nice app, unclear how to use.
does app like Kanban Board App save settings on sys or in app directory?
its kinda local app, is save to use allthough 5years no update?
seem great app, but no manual on github.
i think it will be like open html file with browser, right?
may be a bit bad to set in code but however.
EDIT
i search a offline calendar-kanban app to get finally (all) orginized...
found a list to work through...
https://www.scrumexpert.com/tools/open-source-kanban-tools/
thx