Extremely slow link speed (54Mbits/s) on Linux laptop with 2Gig plan

Just upgraded my gateway from an XB8 to XB10 at the insistence of xfinity due to recent network upgrade.   Phones and windows devices connect fine, but my linux laptops (running Fedora 43) which have been running just fine with the previous gateway, are now crawling... cannot get a download or upload speed greater than 20Mbps.   This is unacceptable.   There are a couple of threads on reddit describing the same issue, so this is not an equipment issue on my side, it is in the gateway.   I had not checked the speeds while on the old XB8 recently, but it was consistently getting >700Mbps on the Linux laptop when I first upgraded to the 2gig plan a few months ago.