As a corollary, I wonder if Slack will now implement calling functionality once Mozilla adds the necessary APIs for Apple to do its job here, which is probably very likely since I don't think Apple chose to ignore a non-Google browser on purpose.

Slack calls didn't used to work on Firefox even if you bypassed their user-agent block.

In recent months, after bypassing the user-agent check, calls will at least work albeit not very well. (bit laggy, long connection time)

All necessary parts are there, which is why e.g. jitsi meet or Google meet work without problem.

It's more like they don't care than anything else.

Slack uses Amazon Chime as backend Chime is using h264 firefox still can not encode h264 videos in real time.

Yes, so it's precisely another case of "we tested on chrome and it works", which falls under "don't care" software development best practices.

Unfortunately, hardware VP9 decoding isn't really well-supported except in high-end phones (in context of multiple decoding, single decoding works fine) due to bugs in Mediatek's implementation. There's software decoding, but that's still taxing to a phone, and transcoding to H.264 server-side but that doesn't bode well to end-to-end encryption.

No, it's very practical. A lot of devices are just too weak to encode anything other than H.264 so that's the one codec you must support.

Other codecs are better, but you have to do more testing and enable those codecs only on calls where all members are using a device that supports it.

> A lot of devices are just too weak to encode anything other than H.264

Not that your point is wrong, but a lot of devices are too weak to encode/decode H264 as well. It's very recent for me to have access to second-hand hardware with H264 support and still i'm in western Europe where it's easier to come by.

Though as the other commenter pointed out, if you can afford to use hardware en/decoders then it's always the better option.

Are you sure you're not thinking of H265?

I'm kinda curious which devices don't support H264

Apple Business Manager recently stopped working in Firefox and that is a basic portal.