Firefox Portable

First post, newbie.
I have Firefox ESR 52 installed on my desktop (for old school reasons, eg Classic Theme Restorer), and would like to try latest Firefox Portable ESR. I would install it to the same 8 GB flashdrive that has my mail client: Thunderbird Portable Legacy 3.1 (great little program, clean functional interface, never any issues). There's over 7 GB of free space on this flashdrive.
Couple of concerns:
Any way to set Firefox Portable to be the default browser which launches when I click on a link in an email in Thunderbird Portable?

Like the title says. I only use Tabliss, Dark Reader and uBlock Origin. These never gave me problems until recently when I updated Firefox Portable to 92.0.1 or somesuch, and, updating to 93 after that didn't make the problem go away. If I close Firefox Portable and open again right away, the addons load normally. The issue could be related to Sandboxie-Plus, as it always occurs after I emptied the sandbox, but it also happens sometimes (sometimes frequently) if I run Firefox Portable unsandboxed.

With the AllowMultipleInstances=true in FirefoxPortable.ini (that's in my C:\FirefoxPortable folder along with the FirefoxPortable.exe file) when I try to open a 2nd instance it gives the same error popup dialog again that I also got a few months ago when I was still on a (slightly) earlier version of Firefox Portable, and that used to be fixed in an updated version until it came back as of 93.0.

firefox extension DownThemAll has been back in action for a while now

so it ( https://portableapps.com/apps/internet/downthemall_extension ) should be listed again as available in the list of https://portableapps.com/apps

I originally posted on Mozilla's help site, they referred me to here:

I'm using Firefox Portable. For some reason, in text fields, firefox will randomly "paste" (for lack of a better term) the localhost into a text field and act like it's pressed enter. It first started when I was typing, but now it can occur when I'm changing tabs and occasionally when I'm doing nothing at all. No other programs on these systems are doing this.

Hi. I have Firefox version 93.0 64 bits as PortableApp. I use a general password to open Firefox. Each time I run PortableApps it insists in upload a "new version" of Firefox despite it is uptodate.

Hi, I feel like a fish out of water here, surrounded on all sides by what is essentially a windows-centric site..I am a dyed in the wool user of that other OS.. Linux, ( Ubuntu).. I am here basically out of sheer frustration..There are so many iterations of portable apps for Windows and yet Linux is lacking.
In particular I have spent days searching for a portable version of Firefox that will run exclusively from a USB..
I have an Appimage of Firefox that runs , mostly from a USB, but it still insists in writing to folders in the home directory on a PC..

I am currently running Firefox Portable 93.0 on Windows 10 Pro x64. For a while now (earlier versions of Firefox Portable) until now I cannot print anything from the browser. All other browsers on my system (Chrome, Edge, Brave) and regular applications print fine. I have combed the internet searching for help but not finding my specific problem. I have repeatedly stopped and started the Spooler service with no luck. Doesn't matter what content I'm trying to print, either. I would very much appreciate some help. Thanks much!

Hi. Can I launch an instance with the specified profile? The "-p" switch doesn't work.

Hi,

I was hoping that 78.14.0esr was released but instead, the new version is firefox 91.1.0esr.

Is there any plan to release 78.14.0esr?

I was using esr because I hate the new interface and the delete of the "vie image" option. So I won't use the 91.1.0esr.

Thanks in advance