On kernel 6.14.8 the command
iw dev devname link
shows a signal level of 0dbm (very strong)
On kernel 6.14.9 the same command shows the signal level at -95dbm.
speedtest.net runs the same for me on either kernel, its just the reporting that seems broken.
Please report as a regression against the kernel.
See How to file a bug :: Fedora Docs