I'm not linuxy and this may be our bug, but try to set gfx.webrender.software.opengl = true (restart required).

The settings gfx.webrender.software.opengl = true does nothing. Compositing stays on webrender "(software)".

What about gfx.webrender.software?

no, it doesn't help :(

See also this bug (fixed for 91).

• 1715902 - Refuse WebRender on Linux if GL context backed by software driver

I've checked the firefox-nightly-91.0a1.20210614215408. It doesn't fix my issue.

I still have the issue with firefox 91. You can take a look at the about:support of my mediacenter here : https://app.box.com/s/dina3cf1fqi4sr8yzxvjeewf7iz6sarc anyone can help me ?

I found some information here .

There does not appear to be any way to turn it off. That is a bit of a shame because it means that GNU/Linux users no longer have the option of enabling the older OpenGL renderer by flipping layers.acceleration.force-enabled to true. That switch does absolutely nothing in Firefox 88+. The OpenGL renderer was never made a default on GNU/Linux even though it was much better than the "Basic" rendering Firefox has defaulted to on GNU/Linux until now, so it is hard to guess if they intentionally removed it as an option or if it is just a unfortunate side-effect of they way they are force-enabling WebRender.

I understand the opengl renderer has been removed since v89. If it is true, what is the alternatives to the tearing workaround  ?

It is false.

to enable the older OpenGL renderer with firefox 89+, you must set : gfx.webrender.force-disabled = true layers.acceleration.force-enabled = true

However, it will not be possible after v92 : https://wiki.mozilla.org/Platform/GFX/WebRender_Where#Linux