Hi,
Good news 😊 : although Canon indeed no longer supports the MP640 on Windows 11, I found that the drivers for Windows 10 installed just fine, also installed MP Navigator EX, and I was able to scan. I can’t comment on printing as I don’t use the MP640 to print anymore
For scanning, an alternative might be to use a software called VueScan, which supports a lot of old devices including the Canon MP640, but I haven’t tried it