I can not let this stand as it is.
The problems are almost all on the provider side, because they think they have to implement something special and break the standard (Throttling or faulty implementations, ...).
I sync for years about 36000 items via WebDav to 6 devices without problems. The functionality may be more limited compared to the JoplinServer, but not 8 out of 10 problems are WebDav related.