Most professions where action/inaction can result in damages will have similar insurance. Some insurance firms even specialize in coverage for professionals.

If your profession has an association or similar group, they should be able to help you find those firms if they exist.

I don’t really get how everyone focuses on the ad-free feature as if it’s the only thing that Sync Ultra provides. It also provides text recognition in images, translation in-app, (both requiring constant server work) and will eventually support push notifications (again requiring server work). On top of that, LJ has stated he wants to work on this app full-time, which is only possible if he earns a living from it.

If those features aren’t interesting to a user, there’s always the one-time ad removal option (I’ll admit which is a bit pricey but per OP’s post, is a one time fee and not a subscription).