Im trying to install Joplin 2.7.15 on Windows 10 or Windows 11, and still getting this type of message without reach our goal. I need help or just a double check to communicate to my users that want this specific version that it can't be installed on Windows 10 or Windows 11 anymore.
The error message suggests that you are trying to use a rather old version of Joplin (March 2022) with sync storage data files created / modified by a newer version. You can see that the program is expecting a storage (profile) version 41 but has found that the actual data files are version 43 (which is current).
As I understand it, if more than one client is connecting to the same file system sync and one of them is upgraded to a newer Joplin version that updates the data storage (profile) version, all other users will have to do the same or they will get this message. So although some users say they specifically need Joplin 2.7.15, one or more of them appears to have upgraded to a newer version. I believe that everyone still using 2.7.15 will get this message, not just new installs.
So it would appear that, no, they cannot use the 2.7.15 version any more. However this is not because 2.7.15 does not work on Windows 10 or 11 but because another user is using a newer version and it has upgraded the sync data to a format that 2.7.15 cannot use.
Apologies, I just had to cross out my comments above for anyone who gets this thread as a search result in the future. For reasons unknown I was wrongly conflating two different things; namely, the storage method on the sync target and the local storage method for each client.