Is it possible or even feasible to use something like Reed-Solomon to build in corruption resilience to the uploaded backup data at a destination file level? Parchive2 is an opensource implementation and available as a command line tool on many platforms. Generating par2 sets along side the backup data would add a (configurable) small amount of size overhead, but I believe would add a lot of mitigation against backup integrity failure. Depending on how much your configured for, par2 could be used to rebuild a broken or missing database or repair backup files very quickly.
I think something like that could certainly be useful but suspect integrating it into Duplicati (the whole flow, not just generating par2 files after a backup is done) would be a huge task.
Do you think it’s something that could be tested as part of a --run-script-after batch?