Try highlighting an account, righclick and a menu should appear with option to open in new tab or new window

Thanks david. Rightclicking on the account is what my muscle memory told me to do, but nothing happens - no menu popup. At least it's not been removed. Double-clicking opens and closes the folder list. Double-clicking a message in the message list opens the message in a new tab. I haven't noticed a similar problem anywhere else so it's unlikely to be a generic shortcut problem.

OK, I'm clueless. You might try in troubleshoot mode, as a menu should appear when you rightlclick on an account. Maybe someone using Linux will see this thread.

Right+click on account -> Open in New Window should work on all OS. If it doesn't, check Error Console after attempt fails.

Thanks Wayne, but no menu pops up. No entry in syslog or Gnome Journal.

The Thunderbird error console is ctrl+shift+J

No entries in the error console either. Deleted Thunderbird from Snap and re-installed it. Moved nothing from the previous installation but re-created accounts from scratch. I started it from the command line and left it do download all emails. The open in new window problem is still there, along with some other odd things when changing Tabs with the keyboard. There are screenfulls of errors in the terminal. Multiple copies of:

[ERROR style::stylesheets::rule_parser] Saw @import rule, but no way to trigger the load

console.error: mail.activity: "onDownloadCompleted: TypeError: can't access property \"activity\", this._syncInfoPerFolder.get(...) is undefined" JavaScript error: resource:///modules/activity/autosync.sys.mjs, line 377: TypeError: can't access property "activity", this._syncInfoPerFolder.get(...) is undefined console.error: mail.activity: "OnDownloadError: Sent of My-email-address\n"

console.warn: mail.setup: ({_message:"Hostname is empty or contains forbidden characters. Only letters, numbers, - and . are allowed.", stack:"Exception@resource:///modules/accountcreation/AccountCreationUtils.sys.mjs:114:3\nMalformedException@resource:///modules/accountcreation/Sanitizer.sys.mjs:245:34\nhostname@resource:///modules/accountcreation/Sanitizer.sys.mjs:115:13\ngetUserConfig@chrome://messenger/content/accountcreation/accountSetup.js:1652:44\nvalidateManualEditComplete@chrome://messenger/content/accountcreation/accountSetup.js:2061:31\nonChangedManualEdit@chrome://messenger/content/accountcreation/accountSetup.js:2030:10\nonChangedInAuth@chrome://messenger/content/accountcreation/accountSetup.js:1993:10\nonchange@about:accountsetup:1:15\nreceiveMessage@resource://gre/actors/SelectChild.sys.mjs:245:21\nreceiveMessage@resource://gre/actors/SelectChild.sys.mjs:483:21\n"})

console.error: mail.activity: "OnDownloadError: OmniOS of My-email-address\n" console.error: mail.activity: "onDownloadCompleted: TypeError: can't access property \"activity\", this._syncInfoPerFolder.get(...) is undefined"

   [This OmniOs folder error repeats many times. It is a historic folder. The Thunderbird version ends with 33 messages with no headers that look as if they are a thread of messages split up, followed by for headerless messages that look like one message from an entirely different folder split up.]
   This is on a brand new install with no filters added. Something is severely wrong. 

Thanks again, David

Thanks David. Someone is looking into this.

Since my last post I have done weekly updates and installed libcanberra-gtk-module. At around 22:50 GMT on 24th Feb I restarted Thunderbird from a terminal window with nohup and with stderr going to a log file. The log file shows: ...$ tail -f /var/log/thunderbird/stdout GTK+ 2.x symbols detected. Using GTK+ 2.x and GTK+ 3 in the same process is not supported.: 'glib warning', file /build/thunderbird/parts/thunderbird/build/toolkit/xre/nsSigHandlers.cpp:201

(thunderbird_thunderbird:152076): Gtk-WARNING **: 23:33:22.104: GTK+ module /snap/thunderbird/995/gnome-platform/usr/lib/gtk-2.0/modules/libcanberra-gtk-module.so cannot be loaded. GTK+ 2.x symbols detected. Using GTK+ 2.x and GTK+ 3 in the same process is not supported. Gtk-Message: 23:33:22.104: Failed to load module "canberra-gtk-module" [GFX1-]: glxtest: libpci missing [GFX1-]: glxtest: libEGL initialize failed [GFX1-]: glxtest: No visuals found [GFX1-]: No GPUs detected via PCI

console.error: gloda.datastore: "got error in _asyncTrackerListener.handleError(): 19: constraint failed" console.error: gloda.datastore: "got error in _asyncTrackerListener.handleError(): 19: constraint failed" console.error: gloda.datastore: "got error in _asyncTrackerListener.handleError(): 19: constraint failed" [ERROR style::stylesheets::rule_parser] Saw @import rule, but no way to trigger the load [GFX1-]: RenderCompositorSWGL failed mapping default framebuffer, no dt console.error: [Exception... "Component returned failure code: 0x805e0006 (NS_ERROR_CONTENT_BLOCKED) [nsIChannel.asyncOpen]" nsresult: "0x805e0006 (NS_ERROR_CONTENT_BLOCKED)" location: "JS frame :: resource:///modules/FaviconLoader.sys.mjs :: load :: line 175" data: no] console.error: [Exception... "Component returned failure code: 0x805e0006 (NS_ERROR_CONTENT_BLOCKED) [nsIChannel.asyncOpen]" nsresult: "0x805e0006 (NS_ERROR_CONTENT_BLOCKED)" location: "JS frame :: resource:///modules/FaviconLoader.sys.mjs :: load :: line 175" data: no] console.error: [Exception... "Component returned failure code: 0x805e0006 (NS_ERROR_CONTENT_BLOCKED) [nsIChannel.asyncOpen]" nsresult: "0x805e0006 (NS_ERROR_CONTENT_BLOCKED)" location: "JS frame :: resource:///modules/FaviconLoader.sys.mjs :: load :: line 175" data: no] [ERROR style::stylesheets::rule_parser] Saw @import rule, but no way to trigger the load [ERROR style::stylesheets::rule_parser] Saw @import rule, but no way to trigger the load [ERROR style::stylesheets::rule_parser] Saw @import rule, but no way to trigger the load

   - repeated