Is the patch still working? I tested with the latest Git version on Ubuntu 20.04.3 LTS (Lubuntu version) but when selecting "Set Up as Standalone Device", entering my French phone number and clicking the button "Send SMS", a new window "CAPTCHA Response Required" is opened but it is blank. I followed the build instructions from https://github.com/signalapp/Signal-Desktop/blob/development/CONTRIBUTING.md and in the Linux console, I can see the error (node:15405) electron: Failed to load URL: https://signalcaptchas.org/registration/generate.html?XXX with error: ERR_ACCESS_DENIED\n(Use electron --trace-warnings ... to show where the warning was created).
I replaced URL content by XXX before sharing it in case in contains private information. If I open the link in a web browser I can see the CAPTCHA but I did not receive an SMS code when completing it, I am just asked to open a signalcaptcha:// link.
The patch was downloaded on https://github.com/signalapp/Signal-Desktop/pull/5473.patch and applied with the command patch -p1 < 5473.patch.
I hope it will be possible to use the desktop app without mobile app in the official version also because not everybody uses Android or iOS.

Update: I forgot to type SIGNAL_ENABLE_HTTP=1 yarn start instead of just yarn start but when I get the SMS code and enter it, I can see the error message HTTPError: Invalid code, please try again. (original: promiseAjax: error response; code: 403). The SMS also mentioned the code is for SIGNAL Staging, does it mean we cannot talk to people that are using Signal on the official build if we use the standalone mode on the desktop app?

@sockbot, this PR has gone stale, but I updated it to work again on my fork at dsanders11/Signal-Desktop@0b59689. It doesn't automatically refresh after successfully verifying, requires closing and start the app again, but it does work to set up the device. Feel free to use that commit to update this PR so it's no longer stale.

@dsanders11 I tested your fork but the app does not load even after restarting it, it keeps saying "Loading..." with the loading animation. In the web console, I noticed an error message: "HTTPError: promiseAjax: error response; code: 401". Do you have a solution?

@baptx closing and reopening should do it. But this that code may have gone stale since it was last tested.

Hello! Could you give a try to standalone registration in the latest beta? I think it might be working!

@indutny-signal Hello, I tried v5.27.0-beta.2 by following the install instructions from https://github.com/signalapp/Signal-Desktop/blob/v5.27.0-beta.2/CONTRIBUTING.md which uses the command yarn generate instead of yarn grunt. After the git clone command, I switched to the tag with the command git checkout tags/v5.27.0-beta.2 (like explained on https://stackoverflow.com/questions/4330610/switch-to-another-git-tag). But I have the same error as in my previous comment, even with the command SIGNAL_ENABLE_HTTP=1 yarn start. This issue could be kept open unless it is fixed.

@baptx can you try installing prebuilt beta using instructions on this page and just click "Setup as Standalone Device" from the File menu (assuming you are on macOS).

@indutny-signal I am using Linux and tried your link, the previous issue does not happen anymore but I cannot see "Setup as Standalone Device" in the File menu, there is only "Set Up as New Device" which does not change anything.

Oh right... It works only in development mode. Sorry for confusion. Did you run commands from this step?

@indutny-signal thanks for sharing the instructions to use the production servers, good to know! But to fix the loading issue, I just had to remove the /home/user/.config/Signal-development/ folder on Linux, like explained on #5623 (comment).

To set up the standalone device, I had to use the fork of @dsanders11 which works, I was able to complete the CAPTCHA and send / receive messages between 2 phone numbers (tested by replacing the Signal-development folder to switch between profiles). The latest beta does not work as a standalone device probably because the contribution dsanders11@0b59689 was not added, so I think this issue can be kept open until it works in the latest development version.
I also found an article explaining how to use Signal without smartphone and the official desktop version without development mode: https://ctrl.alt.coop/en/post/signal-without-a-smartphone/ (using signal-cli, I did not try it yet)

Is there no way to enable the development mode (or at least set up a standalone device) in the official desktop version? In the future, it would be nice to be able to set up a standalone device without having to build the app in development mode, which could be useful for people without IT knowledge that don't have an Android or iOS smartphone. It would also be good to be able to use Signal without phone number because currently if someone loses their phone / it gets stolen or they change the phone number, it could be an issue to continue a conversation. A web version like WhatsApp and Telegram would be welcome also, so we can use Signal without installing an app and even if there is no app for our device.