I'm with Old-Biscuit, I don't bother with the unreliable tank indicators.
When we got the motorhome, I thought that those are priority items but soon discovered that there are much more important things to worry about and spend money on a motorhome.
The fresh water level is easy to see by opening the bay door. In our coach the gray and black tanks hold what fresh water is available. If we are hooked to water only with no sewer hookup available it's easy to see the black tank when flushing the toilet and gray tank when the shower no longer drains.
We tent camped for 40 years and multi-day backpacking trips with no water or electricity. So if those luxuries are not available, nothing has changed other than we have a comfy bed to sleep in.
2004 Holiday Rambler Imperial 40PKD, Cummins ISL 400
2019 Buick Envision AWD