We have been building a local-first browser app (PWA) for personal finance, based on double-entry accounting. https://finbodhi.com/

It's not always offline. We do use online services like firebase for auth and subscription, and some service to fetch commodity prices etc, but rest of the data is stored in browser storage (sqlite) and backed to local disk and dropbox. We also syncs data across devices, always encrypting data in transit. We use Evolu for sync.

For most personal applications, this model seems to fit. If you figure out sync, the development model is actually nicer than web apps. There is no need for dealing with calls over network for each action. It does make some things more difficult. Debugging, migrations etc.

If you go on step further with double-entry accounting you will need to book the "stack" to the "journal" as required by the tax office. I do not see how this should work with you local-first approach, because you cannot really guarantee the correct order. If something is in the "journal" it has to be "canceled", if the action was wrong beforehand. This is an additional booking step and not a "revert" of the previous action. No conflict resolution will help you here. Especially the area of double-entry accounting, is something where I never would choose such an local-first/sync approach. Local-first in the classic desktop app single source of thruth sense, sure, but not this way.