Just stating (for my future self any anyone else) that for the other way around (removing features that were never enabled before) there is code that could handle that [1][2]. In a similar fashion libvirt could try to consider older sources before this change as "ok I accept to not insist on this feature and spawn a guest without", but then you'd end up on the new system with guests that appear to have the very same definition but behaving different - that would (other than not being implemented yet) still sound like asking for even more trouble.
Just stating (for my future self any anyone else) that for the other way around (removing features that were never enabled before) there is code that could handle that [1][2]. In a similar fashion libvirt could try to consider older sources before this change as "ok I accept to not insist on this feature and spawn a guest without", but then you'd end up on the new system with guests that appear to have the very same definition but behaving different - that would (other than not being implemented yet) still sound like asking for even more trouble.
[1]: https:/ /gitlab. com/libvirt/ libvirt/ -/commit/ 52cbfb2186364b1 ab64f56e1360dcb c7d8ab85c1 /gitlab. com/libvirt/ libvirt/ -/commit/ 7e0a3104982c5ba 273316d6e39184d 28c9f2fc9a
[2]: https:/