QUOTE:
QuoteMedia provider requires reloading accumulated QuoteMedia data after a split, too

To put this information in one place, I would just like to confirm which data providers are set up to adjust accumulated data for a new stock split and which ones need to have the data deleted and reloaded. This is my understanding, please correct me if I'm wrong about any of the providers:

Fidelity - No need to reload data
Morningstar - NEED TO DELETE AND RELOAD ALL DATA
NASDAQ - NEED TO DELETE AND RELOAD ALL DATA
QuoteMedia - NEED TO DELETE AND RELOAD ALL DATA
Tiingo - No need to reload data (?)
Wealth-Data - No need to reload data
Yahoo - No need to reload data

The providers, especially Yahoo, may make corrections to the most recent bars (to correct errors not necessarily related to stock splits) which are automatically applied when Data Manager updates the data. The providers also may make corrections to older bars from time to time, and the only way to get those corrections is to delete and reload your existing data.

That's right and then some:

AlphaVantage - no need to reload data
IQFeed - most likely need to reload data
Dukascopy, Nasdaq (incl. Nordic), Stooq - need to reload data
Finam, MFD - need to reload data but Russian stocks almost never split
Quandl - most likely no need to reload data

Other providers for Forex, sentiment and cryptos obviously have no need in data reload as these assets don't split.