So we’re running different kernels, even curiouser and curiouser. :)

You’re right that the one you currently have probably has been the only one it’s had since installing (judging from 6.14’s publishing history).

Could you check to see which updates, if any, you’ve installed just prior to the lockups starting? The log files should be under /var/log/apt/ as history.log (the most recent), then history.1.gz (next newest) etc. The .log files are plain text. The .gz ones are compressed, so have to be decompressed first, or, if you’re comfortable with the command line, you can use zless to view them directly.

To me this does look like a kernel issue, but if any non-kernel updates are the trigger, you could perhaps work around the issue by downgrading the package(s), if you can pinpoint which one(s) started the issue.