03Feb25 UPDATE:
1. Bad commits in 6.6.72 fixed in next kernel, although .73 & .74 seem to have other issues.
No, my debian configs at fault, so changed.
2. Issue with Debian config 6.6.72+ - drive names seem to vary on boot (emmc drive).
No, my debian configs at fault, so changed.
3. 6.11+ doesn't allow some firmware to fall back to earlier versions, requiring the latest.
- iwlwifi seems most affected.
4. wl driver source needs a hack to compile in 6.12 . 6.13 needs an extra (dubious) hack.
- I guess if a pc is old enough to have a broadcom wl chip, probably too old for 6.13+.
Solution from BarryK - fixed.
26 Feb 2025 - 3 solved (2 by using modified x-series = m-series kernels) - 1 we have to live with.