Firefox not taking focus when opening links from (EDIT) some apps but not others on Wayland (KDE)

Dunno if this is Wayland, Thunderbird, Firefox or KDE causing this issue but in the past few days I've been giving Wayland a go. Been much snappier and no issues but for Firefox not taking focus when I open web links in Thunderbird.

When I use Thunderbird with X and click on a link, Firefox will correctly grab focus and open the link.

Using Wayland, clicking a link in Thunderbird correctly opens the link in Firefox however Firefox stays minimised or drawn behind the other windows. My dock (KDE panel set to "Windows can cover") also does not pop up like it normally would if I've opened something but it's in the background. It stays hidden and I have to mouse over it to see that the Firefox icon is highlighted.

I've tried opening links from the Steam client and Firefox correctly takes focus from there so it so far seems to be just Thunderbird links not opening correctly in Firefox. I haven't been able to find anything in KDE's settings that would affect only Thunderbird.

EDIT (tested some different app combos):

Applications it correctly takes focus from: Pamac, Bottles, Calibre, Gnome Calculator, Gnome Evince Document Viewer, Steam, Strawberry Music Player

Applications it doesn't grab focus from: Thunderbird and Betterbird, Libreoffice (links in the About or URL links in a document), GIMP, Krita, Signal, Kdenlive, Darktable, VLC, QtAV QMLPlayer, Obsidian

I also tried Okular links but for some reason those opened in Chromium instead of Firefox (despite Firefox being set to default) but Chromium did take focus.

It's a minor annoyance but obviously I would like to fix it if possible and continue using Wayland given that, for me, it's noticeably faster than X.

OS: Arch Linux x86_64
Kernel: 6.6.10-arch1-1
DE: Plasma 5.27.10
WM: kwin
Display Server: Wayland 1.22.0-1
GPU: AMD ATI Radeon RX 6800 XT

Thunderbird 115.6.1, Firefox 121.0.1.

TIA!