A quick question: how do I grant extensions like Adblock and Ghostery necessary permissions in the template so it would not show me slpash screens and ask for permissions every time?
It will depend on how well these extensions support Firefox policies. uBlock Origin has good support, so you can look to it as an example. A good place to start is:
Also search âFirefox policyâ on the github site for each extension (if they have one). The following page has links to several additional resources:
Does not seem relevant there 
Maybe there are some entries but they are not documented apparently.
One way would be to customize browser in an offline dispVM, then copy browserâs profile to templateâs skel direcotry, then create new dvm-template.
Adblock and Ghostery are no longer recommended for privacy (mainely because of their new owners).
As suggest by @ephile, Ublock origin is all what you need. (ghostery is also redundant with ublock origin).
Another good strarting points:
https://www.privacyguides.org
https://www.privacytools.io/
A bit offtopic and not Qubes specific, but as you seem to use Adblock, it was necessary to be told.
edit: add original project, privacytools dot io
The best way to customize Firefox for disposable vms is with policies, but outside of Qubes Firefox policies are primarily used in an enterprise setting. Outside of uBlockâs links, your best bet is probably to directly ask each extensionâs devs if they support enterprise policies and how to eliminate the splash screen using policies.
I will âsecondâ arkenoiâs question.
If I want to use the download manager it insists on throwing up a âcongratulationsâ webpage every time I start firefox. Utterly pointless and damned annoying because of that.
I hope I donât completely miss the mark here, but it seems to me that starting the DVM Template
Start - Qube Tools - Qube Manager - DVM - Start
Then selecting it in the Qube Domains Icon in your task bar and opening a terminal within it to execute the commands to install arkenfox in it would work without the hassle of configuring exceptions.
You can also start Firefox via the command line, add extensions, click through annoying messages etc. After you have modified the Browser to your liking, shut down the DVM-Template and the changes you made should persist.
Of course, youâld need to take these steps every time you want to update an extension or change something in Firefox, but it seems to me that thatâs kind of the idea behind a DVM.
Setting up Firefox in the DVM template has some advantages, but the downside is that every disposable vm spawned with that template will share the same Firefox profile. Firefox policies allow one to set parameters for extensions (that support such policies), without creating a fixed profile for the DVM template. So there are tradeoffs to be madeâŚ
1 Like