ETFbitcoin -- thanks for the suggestion. I tried moving all the files inside the "index" folder then running Bitcoin Core with -reindex but it immediately abended with the same error as before. Here is the log created by my attempt to follow your suggestion:
2022-09-02T17:45:41Z init message: Loading block index…
2022-09-02T17:45:41Z Switching active chainstate to Chainstate [ibd] @ height -1 (null)
2022-09-02T17:45:41Z Wiping LevelDB in F:\Bitcoin\blocks\index
2022-09-02T17:45:41Z boost::filesystem::status: Access is denied: "F:\Bitcoin\blocks\index"
2022-09-02T17:45:41Z Error: Error opening block database
While all logs have same error message "Error: Error opening block database", it's caused by different reason. Last time it was caused by "Fatal LevelDB error", but this time is "boost::filesystem::status: Access is denied".
Try editing the NAS partitions access control settings and selecting for the group "Everyone": "Read" and "Write" permissions (I think there is a "Full control" mode that should be used instead of those previous two, that will solve all access control problems).