Presumably you'll need to either use the correct WAL file or accept some very slight data staleness during the 9.0 sync process (also the direct read trick sounds great to me where permissible - EDIT: question about how much of your warranty does that void removed because the answer's already written up here - https://rqlite.io/docs/faq/#can-i-read-the-sqlite-file-direc...).

I would -imagine- that 'slight staleness' won't matter for your use case (I'm pretty confident that for the sort of configs I'm considering rqlite for that'll be the case, at least) but it's probably worth triple checking when configs are involved.