Enabling chromium's reader mode in about:flags does not work

[ghost]

Description

Enabling (#enable-reader-mode) flag does not work. The reason I want to do this is because speedreader is not finished yet, and does not work on most sites I want to use it on.

Steps to Reproduce

1. Enable #enable-reader-mode in about:flags
2. Go on a news site article (example: nytimes.com)

Actual result:

Reader mode does not show up, unlike in chromium (also with the flag manually enabled). As shown in the screenshot.

Expected result:

Chromium's reader mode should show up.

Reproduces how often:

Every time on an article where chromium would show it.

Brave version (info found on brave://version)

Brave	1.23.73 Chromium: 90.0.4430.85 (Official Build) (64-bit)
Revision	5bc145d831c180d9ff94f29a0d7a2e1cbd30ef36-refs/branch-heads/4430@{#1311}
OS	Windows 10 OS Version 2009 (Build 19042.928)

Version/Channel Information:

• Can you reproduce this issue with the current release? yes
• Can you reproduce this issue with the beta channel? yes
• Can you reproduce this issue with the dev channel? haven't checked
• Can you reproduce this issue with the nightly channel? yes

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields? no
• Does the issue resolve itself when disabling Brave Rewards? no
• Is the issue reproducible on the latest version of Chrome? no

Miscellaneous Information:

[ghost]

It also does not show up in the hamburger menu, unlike chromium where it does.

[MetotoSakamoto]

No icon at all here with flatpak version too

[dentistformyeye]

In MacOS, it's in the top menu: View > Enter Reader Mode.

It only works on certain pages though: #11994 (comment)

[illtellyoulater]

Can confirm.
No signs of "reader-mode" after enabling the flag and relaunching the browser...
I'm using latest version on Windows 10.

[rebron]

Closing. Chromium's reader mode is available as subset of Speedreader and available via: brave://flags/#brave-speedreader to turn by everybody or enabled and rolled out to some users by default via the SpeedreaderReleaseStudy. https://griffin.brave.com/ You can see if you're in that study by looking at brave://versions

See #11994 as what we're working on next.