[clementmas]

As someone pointed out, it's indeed harder to animate but it's fully accessible, supports escape key to close, has a built-in backdrop and has built-in focus trap. Safari took a while to support it but now it's available everywhere. I think it's better than using a <div> tag.

[tomsmeding]

Apparently it's unsupported in the Firefox ESR version in Ubuntu 20.04, which still receives support from Canonical until 2025. I found that out because someone reported that my site didn't work.

[chrismorgan]

This doesn’t sound right at all.

Ubuntu itself doesn’t have an ESR package, only https://packages.ubuntu.com/focal/firefox which is at 125.

The Mozilla PPA does have an ESR package, but per https://launchpad.net/~mozillateam/+archive/ubuntu/ppa?field... it’s at 115.

<dialog> has been supported since Firefox 98, meaning ESR 91 was the last release lacking it, and it reached end of support over a year and a half ago.