Browser integration not working (Linux Firefox)

[arrhat]

I've followed the steps in the troubleshooting document, but I cannot get KeePassXC to integrate with Firefox. (That said, I am very new to Linux so apologies if this is a user error on my end.) The KeyPassXC browser extension gives me the error "Cannot connect to KeePassXC. Check that browser integration is enabled in KeePassXC settings."

• I'm running Kubuntu 24.10, Firefox 133.0, and KeePassXC 2.7.9. I have the KeePassXC browser extension installed and browser integration enabled for Firefox in KeePassXC.
• I'm using the Firefox snap install because my understanding is that Kubuntu shares the same repositories as Ubuntu, so this should be the supported version. (Is this incorrect? I would prefer the snap install for the convenience of managing installations through the KDE Discover panel, but if I've just misunderstood the relation between Ubuntu and Kubuntu please let me know.)
• The org.keepassxc.keepassxc_browser.json file is in the correct location and configured correctly.
• I can't find keepassxc-proxy, but org.keepassxc.keepassxc_browser permission is set to yes.
• Extension debugging log doesn’t show anything useful, as far as I can tell:

KeePassXC-Browser: Connecting to native messaging host org.keepassxc.keepassxc_browser client.js:383:13
[Error ] KeePassXC-Browser - Failed to connect: Unknown error global.js:168:13
[Error ] KeePassXC-Browser - No content script available for this tab. global.js:168:13
[Error keepass.js:256] KeePassXC-Browser - 5: Cannot connect to KeePassXC. Check that browser integration is enabled in KeePassXC settings. global.js:168:13
[Error ] KeePassXC-Browser - Cannot send activated_tab message: Could not establish connection. Receiving end does not exist. 3 global.js:168:13

• I followed the steps in the linked blog post to check for extension conflicts (even though I have no other extensions installed). The log text doesn't mean anything to me, but here it is:

MOZ_LOG=NativeMessagingPortal:5 snap run firefox
[26676, Main Thread] WARNING: Theme parsing error: gtk.css:1:21: Failed to import: Error o
pening file /home/raven/snap/firefox/5361/.config/gtk-3.0/colors.css: No such file or dire
ctory: 'glib warning', file /build/firefox/parts/firefox/build/toolkit/xre/nsSigHandlers.c
pp:201

(firefox:26676): Gtk-WARNING **: 21:59:11.195: Theme parsing error: gtk.css:1:21: Failed t
o import: Error opening file /home/raven/snap/firefox/5361/.config/gtk-3.0/colors.css: No
such file or directory
[Parent 26676: Main Thread]: D/NativeMessagingPortal NativeMessagingPortal::NativeMessagin
gPortal()
[Parent 26676: Main Thread]: D/NativeMessagingPortal will be used
[Parent 26676: Main Thread]: D/NativeMessagingPortal NativeMessagingPortal::DelayedCall::D
elayedCall()
[Parent 26676: Main Thread]: D/NativeMessagingPortal D-Bus proxy ready for name org.freede
sktop.portal.Desktop, path /org/freedesktop/portal/desktop, interface org.freedesktop.port
al.WebExtensions
[Parent 26676: Main Thread]: D/NativeMessagingPortal is available
[Parent 26676: Main Thread]: D/NativeMessagingPortal NativeMessagingPortal::DelayedCall::~
DelayedCall()
[Parent 26676: Main Thread]: D/NativeMessagingPortal creating session with handle suffix f
irefox_org_keepassxc_keepassxc_browser_2397937349
[Parent 26676: Main Thread]: D/NativeMessagingPortal session created with handle /org/free
desktop/portal/desktop/session/1_187/firefox_org_keepassxc_keepassxc_browser_2397937349
[Parent 26676: Main Thread]: D/NativeMessagingPortal manifest found in session /org/freede
sktop/portal/desktop/session/1_187/firefox_org_keepassxc_keepassxc_browser_2397937349: {"a
llowed_extensions":["[email protected]"],"description":"KeePassXC integratio
n with native messaging support","name":"org.keepassxc.keepassxc_browser","path":"/usr/bin
/keepassxc-proxy","type":"stdio"}
[Parent 26676: Main Thread]: D/NativeMessagingPortal starting org.keepassxc.keepassxc_brow
ser, requested by [email protected] in session /org/freedesktop/portal/deskt
op/session/1_187/firefox_org_keepassxc_keepassxc_browser_2397937349
[Parent 26676: Main Thread]: D/NativeMessagingPortal native application start requested in
session /org/freedesktop/portal/desktop/session/1_187/firefox_org_keepassxc_keepassxc_bro
wser_2397937349, pending response for /org/freedesktop/portal/desktop/request/1_187/firefo
x/1430778884
[Parent 26676: Main Thread]: D/NativeMessagingPortal got response signal for /org/freedesk
top/portal/desktop/request/1_187/firefox/1430778884 in session /org/freedesktop/portal/des
ktop/session/1_187/firefox_org_keepassxc_keepassxc_browser_2397937349
[Parent 26676: Main Thread]: D/NativeMessagingPortal native application start canceled by
user in session /org/freedesktop/portal/desktop/session/1_187/firefox_org_keepassxc_keepas
sxc_browser_2397937349
[Parent 26676: Main Thread]: D/NativeMessagingPortal session /org/freedesktop/portal/deskt
op/session/1_187/firefox_org_keepassxc_keepassxc_browser_2397937349 was closed by the port
al
[Parent 26676: Main Thread]: D/NativeMessagingPortal cannot close session /org/freedesktop
/portal/desktop/session/1_187/firefox_org_keepassxc_keepassxc_browser_2397937349, unknown
handle

Any assistance appreciated. Thank you!

[droidmonkey]

Last I tested Firefox snap it was broken. They did something to break native messaging. There isn't anything we can do about that until they fix it.

[arrhat]

OK, thank you, I'll move on from trying to get it to work. Sorry for troubling folks with a trivial issue, and thank you for responding anyway.

As a very minor followup: the troubleshooting guide currently states that Ubuntu's snap install of Firefox is supported; if that's not correct then someone may want to update it.

[droidmonkey]

It's supported and worked fine, but something broke outside our control.