backport-iwlwifi-dkms version 8324 breaks Intel Wi-Fi 6 AX200 (rev 1a)

[Sergio Callegari]

Seen on a Schenker Slim 14 ed 2019 laptop (that is probably a Clevo N141-CU).

Upgrading from eaon to focal has broken the wifi performance.
Wifi seems to connect properly, ping to sites is OK-eish, but on real workload the performance is gone. For instance web browsers seem to hang forever and speed tests tend to hang on the "upload side".

Removing the backport-iwlwifi-dkms package restores performance.

With the package installed there are many entries in the system logs with complaints about inability to correctly upload firmware, these could just be multiple attempts with different files, so I don't know if they are really an issue or not:

iwlwifi 0000:40:00.0: Direct firmware load for iwl-dbg-cfg.ini failed with error -2
[ 4.783339] iwlwifi 0000:40:00.0: Direct firmware load for iwlwifi-cc-a0-55.ucode failed with error -2
[ 4.783361] iwlwifi 0000:40:00.0: Direct firmware load for iwlwifi-cc-a0-54.ucode failed with error -2
[ 4.783379] iwlwifi 0000:40:00.0: Direct firmware load for iwlwifi-cc-a0-53.ucode failed with error -2
[ 4.783397] iwlwifi 0000:40:00.0: Direct firmware load for iwlwifi-cc-a0-52.ucode failed with error -2
[ 4.783635] iwlwifi 0000:40:00.0: Direct firmware load for iwlwifi-cc-a0-51.ucode failed with error -2
[ 4.783655] iwlwifi 0000:40:00.0: Direct firmware load for iwlwifi-cc-a0-50.ucode failed with error -2
[ 4.783672] iwlwifi 0000:40:00.0: Direct firmware load for iwlwifi-cc-a0-49.ucode failed with error -2
[ 4.784899] iwlwifi 0000:40:00.0: TLV_FW_FSEQ_VERSION: FSEQ Version: 43.2.23.17
[ 4.784902] iwlwifi 0000:40:00.0: Found debug destination: EXTERNAL_DRAM
[ 4.784904] iwlwifi 0000:40:00.0: Found debug configuration: 0
[ 4.785164] iwlwifi 0000:40:00.0: loaded firmware version 48.4fa0041f.0 cc-a0-48.ucode op_mode iwlmvm
[ 4.785278] iwlwifi 0000:40:00.0: Direct firmware load for iwl-debug-yoyo.bin failed with error -2

and then

iwlwifi 0000:40:00.0: Applying debug destination EXTERNAL_DRAM
[ 169.267900] iwlwifi 0000:40:00.0: FW already configured (0) - re-configuring
[ 169.271268] iwlwifi 0000:40:00.0: BIOS contains WGDS but no WRDS

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: backport-iwlwifi-dkms 8324-0ubuntu1
ProcVersionSignature: Ubuntu 5.4.0-31.35-generic 5.4.34
Uname: Linux 5.4.0-31-generic x86_64
ApportVersion: 2.20.11-0ubuntu27
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: KDE
Date: Sat May 23 19:54:10 2020
EcryptfsInUse: Yes
InstallationDate: Installed on 2020-02-16 (97 days ago)
InstallationMedia: Kubuntu 19.10 "Eoan Ermine" - Release amd64 (20191017)
PackageArchitecture: all
SourcePackage: backport-iwlwifi-dkms
UpgradeStatus: Upgraded to focal on 2020-05-23 (0 days ago)