(Topic moved here and 'Etcetera organs' appended to its title, so that people can find it more easily.)
There's no way to use encrypted v4 sample sets in v5+ directly, I'm afraid -- the producer needs to have re-encrypted them for v5+. See also this post re. Etcetera organs:
viewtopic.php?f=1&t=20415&p=153223#p153223
mdyde wrote:Based on a search of the forum, it does appear that the last status update on that one (from February 2021) was that Magne (the sample set creator) intended to release it in v5+ format, but hadn't yet had time to do it:
viewtopic.php?f=6&t=18978
viewtopic.php?f=6&t=19486
I haven't heard anything from him since then (or directly since v5 was released), so I imagine that might still apply, in which case his sample set(s) might indeed not yet be available for v5+ ..., but hopefully he'll have a chance to get to it eventually.