After the FF 96 upgrade I can't distinguish focused and unfocused FF windows from their client side decorations.
Previously the distinction was subtle, but not impossible.
The attached image shows two windows, the one on the left has focus. The only way you can tell this is that the scrollbar is faded in the unfocused window.
ProblemType: Bug
DistroRelease: Ubuntu 21.10
Package: firefox 96.0+build2-0ubuntu0.21.10.1
Uname: Linux 5.14.0-051400-generic x86_64
AddonCompatCheckDisabled: False
ApportVersion: 2.20.11-0ubuntu71
Architecture: amd64
BuildID: 20220106144528
CasperMD5CheckResult: unknown
Channel: Unavailable
CurrentDesktop: ubuntu:GNOME
Date: Fri Jan 14 13:15:27 2022
DefaultProfileExtensions: extensions.sqlite corrupt or missing
DefaultProfileIncompatibleExtensions: Unavailable (corrupt or non-existant compatibility.ini or extensions.sqlite)
DefaultProfileLocales: extensions.sqlite corrupt or missing
DefaultProfilePrefErrors: Unexpected character ',' before close parenthesis @ /usr/lib/firefox/omni.ja:greprefs.js:365
DefaultProfilePrefSources: prefs.js
DefaultProfileThemes: extensions.sqlite corrupt or missing
ForcedLayersAccel: False
IfupdownConfig:
# interfaces(5) file used by ifup(8) and ifdown(8)
auto lo
iface lo inet loopback
InstallationDate: Installed on 2019-06-18 (941 days ago)
InstallationMedia: Ubuntu 19.04 "Disco Dingo" - Release amd64 (20190416)
ProcEnviron:
TERM=tmux-256color
PATH=(custom, no user)
XDG_RUNTIME_DIR=<set>
LANG=en_US.UTF-8
SHELL=/bin/bash
Profile1Extensions: extensions.sqlite corrupt or missing
Profile1IncompatibleExtensions: Unavailable (corrupt or non-existant compatibility.ini or extensions.sqlite)
Profile1Locales: extensions.sqlite corrupt or missing
Profile1PrefErrors: Unexpected character ',' before close parenthesis @ /usr/lib/firefox/omni.ja:greprefs.js:365
Profile1PrefSources: prefs.js
Profile1Themes: extensions.sqlite corrupt or missing
Profile2Extensions: extensions.sqlite corrupt or missing
Profile2IncompatibleExtensions: Unavailable (corrupt or non-existant compatibility.ini or extensions.sqlite)
Profile2Locales: extensions.sqlite corrupt or missing
Profile2PrefErrors: Unexpected character ',' before close parenthesis @ /usr/lib/firefox/omni.ja:greprefs.js:365
Profile2PrefSources: prefs.js
Profile2Themes: extensions.sqlite corrupt or missing
Profiles:
Profile1 - LastVersion=96.0/20220106144528 (In use)
Profile0 (Default) - LastVersion=96.0/20220106144528 (In use)
Profile2 - LastVersion=71.0/20191205203726 (Out of date)
RebootRequiredPkgs: Error: path contained symlinks.
RunningIncompatibleAddons: False
SourcePackage: firefox
UpgradeStatus: Upgraded to impish on 2021-10-31 (75 days ago)
dmi.bios.date: 11/27/2019
dmi.bios.release: 5.14
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: P2.90
dmi.board.name: B450M Steel Legend
dmi.board.vendor: ASRock
dmi.chassis.asset.tag: To Be Filled By O.E.M.
dmi.chassis.type: 3
dmi.chassis.vendor: To Be Filled By O.E.M.
dmi.chassis.version: To Be Filled By O.E.M.
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrP2.90:bd11/27/2019:br5.14:svnToBeFilledByO.E.M.:pnToBeFilledByO.E.M.:pvrToBeFilledByO.E.M.:skuToBeFilledByO.E.M.:rvnASRock:rnB450MSteelLegend:rvr:cvnToBeFilledByO.E.M.:ct3:cvrToBeFilledByO.E.M.:
dmi.product.family: To Be Filled By O.E.M.
dmi.product.name: To Be Filled By O.E.M.
dmi.product.sku: To Be Filled By O.E.M.
dmi.product.version: To Be Filled By O.E.M.
dmi.sys.vendor: To Be Filled By O.E.M.
What is the value of your system theme reported in about:support ?
On my system where the value is "Yaru / Yaru", I can see a difference in the title bar color between focused and unfocused windows, so it's probably a theme-specific problem.