make the old questions dupes of the new one

I don't like that, because they aren't duplicates. You say yourself that

the landscape has changed dramatically

declaring something a duplicate that is "dramatically" different doesn't work for me.

I think the ideal solution is to lock them with a historic lock. As it looks, this is not the original purpose of such a lock, but it fits the situation perfectly.

I propose that:

When a good question becomes obsolete and/or its answers become obsolete due to advancements in technology, the question gets a historic lock. It is explicitly not a duplicate of newer "versions" of that question, because the context changed. When the time is right for this lock is difficult. The "time" of the question is mostly determined by the period in which the answers were given (which can be continuously added). The question should be locked when most of the answers become obsolete.

The question should be marked as a historic lock, so that people are aware of it being "old" content.

I agree that it can be a good idea to link to a newer version, so that people that find the old question can quickly find the current one.

tl;dr

It's not a duplicate, so let's not make it a duplicate. A historic lock + optional links to current question(s) appears to be more appropriate. I am aware that it is almost the same thing.

make the old questions dupes of the new one

I don't like that, because they aren't duplicates. You say yourself that

the landscape has changed dramatically

declaring something a duplicate that is "dramatically" different doesn't work for me.

I think the ideal solution is to lock them with a historic lock. As it looks, this is not the original purpose of such a lock, but it fits the situation perfectly.

I propose that:

When a good question becomes obsolete and/or its answers become obsolete due to advancements in technology, the question gets a historic lock. It is explicitly not a duplicate of newer "versions" of that question, because the context changed. When the time is right for this lock is difficult. The "time" of the question is mostly determined by the period in which the answers were given (which can be continuously added). The question should be locked when most of the answers become obsolete.

The question should be marked as a historic lock, so that people are aware of it being "old" content.

I agree that it can be a good idea to link to a newer version, so that people that find the old question can quickly find the current one.

tl;dr

It's not a duplicate, so let's not make it a duplicate. A historic lock + optional links to current question(s) appears to be more appropriate. I am aware that it is almost the same thing.