Firefox snap cannot be added to dock while transitional deb is installed

[Lem]

I finally figured out why I couldn't add my firefox snap to the dock - having the transitional deb file installed at the same time as the snap prevents the dock from correctly recognising the firefox snap (assuming because both contain a firefox.desktop file?). Removing the transitional deb makes it work again.

Steps to reproduce:
1. Install Firefox snap (snap install firefox).
2. Install Firefox deb (apt-get install firefox).
3. Press Super, type Firefox, right click and add Firefox to favourites (appears on dock).
4. Left click on Firefox icon on dock to start it.
5. Observe that there are now two Firefox icons on the dock.
6. The originally pinned Firefox icon is functional, but always opens new windows, never gets recognised as being already opened.
7. Quit Firefox.
8. Remove Firefox from favourites.
9. Remove deb (apt-get remove firefox).
10. Repeat Step 3 and 4, observe that the Firefox dock icon functions as expected.

ProblemType: Bug
DistroRelease: Ubuntu 22.04
Package: firefox 1:1snap1-0ubuntu2
Uname: Linux 6.4.8-1-liquorix-amd64 x86_64
ApportVersion: 2.20.11-0ubuntu82.5
Architecture: amd64
CasperMD5CheckResult: unknown
CurrentDesktop: ubuntu:GNOME
Date: Tue Aug 8 20:00:00 2023
InstallationDate: Installed on 2020-12-12 (968 days ago)
InstallationMedia: Ubuntu 20.04.1 LTS "Focal Fossa" - Release amd64 (20200731)
Snap.Changes:
 ID Status Spawn Ready Summary
 1213 Done 2023-08-08T19:31:42+08:00 2023-08-08T19:32:13+08:00 Refresh snaps "firefox", "signal-desktop"
SourcePackage: firefox
UpgradeStatus: Upgraded to jammy on 2022-04-22 (473 days ago)