Problems with Slackware-15.0, Firefox, and QUIC (HTTP3) sites?
 

This might have started when Slackware-15 upgraded to firefox-115.7.0ESR. Or maybe not. One specific financial site no longer works - pages lock up for several minutes, sometimes they eventually recover, sometimes stopping and reloading works. The site is hosted on cloudfront.net and I noticed with Wireshark it is using QUIC (http3). Turning off network.http.http3.enable in Firefox completely fixes it. Is anyone seeing anything like this?

tested QUIC here:
https://quic.nginx.org/
works fine in FF 115.7.0 esr with network.http.http3.enable turned on. If you disable quic then probably you are loading an alternate web page without quic as http3 is not yet established so your site may have both with quic and without quic site.

Yep. Same here. Works fine.

Works here as well

Thanks, all. That test site works fine for me too ("Congratulations - You're connected over QUIC"). Yet the site I'm trying use (a financial site where I have accounts) fails with QUIC on. Doesn't seem to be too much I can do about it, especially since everything seems to work well with HTTP3 disabled. I suppose I could call them up, if I want to hear them say "we don't support Linux", or "try using Microsoft Edge or Google Chrome instead".

There's a test on the site which sends a few thousand packets. That also worked for me.

Firefox 115.7.0 esr worked on these sites too:
https://http3.is/#
https://cloudflare-quic.com/
https://quic.tech:8443/
https://quic.rocks:4433/
https://quic.aiortc.org/

list of implementations of http/3 and tests. Not All are working (some seems abandonned)
https://bagder.github.io/HTTP3-test/

I did not know that there are so many implementations of http/3

Do you need to attempt to login to see the error?
Or do you get it when you access the base URL -> (https://www.somesite.com)?

If the later, are you comfortable sharing the base URL for the site?