[Documentation] dist/README Chromium manual install: clarify MV2 (uBlock0.chromium) vs MV3-only browsers

[th3w1zard1]

Type

Documentation — not a uBlock Origin code bug.

Summary

Following README → Manual Installation → dist#chromium on Fedora 44 + Flatpak Chromium 148 leads users to load uBlock0.chromium (Manifest V2). Chromium 148 is MV3-only, so the browser correctly rejects the extension:

Failed to load extension
Cannot install extension because it uses an unsupported manifest version.
Could not load manifest.

The root README table mentions "End of support on Chrome 139" for the store row, but the manual install page does not explain MV2 vs MV3, what uBlock0.chromium is, or what to do on current Chromium. That gap caused this report to be filed as a product bug.

What we tried (repro context)

• Release uBlock0_1.71.0.chromium.zip — manifest_version: 2
• make chromium on master — same MV2 output
• Browser: Chromium 148.0.7778.96 via Flatpak org.chromium.Chromium on Fedora 44 KDE Plasma

Requested change

Clarify in dist/README.md (Chromium / manual install) and cross-link from README.md (Chromium section):

1. GitHub releases + make chromium = MV2 (uBlock0.chromium).
2. Chromium ~139+ rejects MV2 → the error above is expected, not a corrupt build.
3. Pointers for current Chromium users: Web Store (if available), Firefox for full uBO, or make mv3-chromium / uBO Lite for unpacked MV3 (separate product; uBOL tracker).

Proposed doc patch (local draft)

Reporter prepared wording in a fork/clone; happy to open a PR to gorhill/uBlock if maintainers want it. Key addition is a "Manifest V2 vs Manifest V3 (read this first)" section at the top of dist/README.md#chromium.

Related

• #3563 — MV2 removal / Chrome "no longer supported"
• #3860 — same error on Canary (closed as external/invalid; same underlying MV2 vs MV3 mismatch)

Environment (for reproducibility only)

Item	Value
OS	Fedora Linux 44 (KDE Plasma)
Browser	Chromium 148.0.7778.96 (Flatpak org.chromium.Chromium)

Screenshot of the Chromium error dialog available on request (reporter can attach).

[th3w1zard1]

Clarification (reporter): This is not asking for uBO to change behavior on Chromium 148. The browser is MV3-only; uBlock0.chromium is MV2 by design.

The actionable ask is documentation: the manual install page should state upfront that releases/make chromium are MV2, that current Chromium rejects them with unsupported manifest version, and where to go instead (store, Firefox, make mv3-chromium / uBO Lite).

Draft text prepared locally for dist/README.md and README Chromium section — willing to submit a PR to gorhill/uBlock if maintainers want it.