I am also using iOS with Möbius Sync and it is working quite well. The sync is not running all the time in the background due to iOS restrictions but it is running multiple times per day on my device.
The option to sync folders was only introduced this year. It costs about 5$ one time payment.
There will be many conversion tools for Joplin to other structures. So I guess the format is a non issue.
There will always be cases of collateral damage. You won’t be able to safe the climate in such a big and complex society without disadvantaging some people.
Maybe one possibility for your wife could be to measure the cleaning equipment and see if it might fit into a smaller car and potentially buy cleaning equipment that is more foldable that might fit. Usually even these small cars have a lot of space when using the back seat row. A big vacuum and mops should easily fit. If this is not possible then I completely understand your problem.
The bigger issue I see with this is that, when your wife would do everything to save gas, she would need to take some disadvantages, e.g., more uncomfortable to load the small vehicle. If there is no pressure for other people, she would be the only one doing it, making it unfair. That’s why it is so important to generate pressure on climate damaging behaviour on all fronts. And this action is one efficient and realistic way to achieve that. But of course you can make the movement more unpopular in the general population… It is really difficult to find and decide for a solution here…
The issue is that an SUV is probably never needed, therefore everyone can trade it in for a more reasonable car.
iOS has Möbius Sync as a Syncthing client, but it is not free ( but only 5$ one time payment) if you want to sync folders from other apps like Syncthing. The option to sync other folders was introduced this year.