Can't access lutris.net in Firefox

[HolyBlackCat]

This is similar to lutris/lutris#4363

I can access https://forums.lutris.net/ but not https://lutris.net. This only happens in Firefox, both sites work in Chrome.
traceroute also fails:

traceroute to lutris.net (104.21.96.1), 30 hops max, 60 byte packets
 1  _gateway (192.168.100.1)  8.010 ms  8.124 ms  8.333 ms
 2  147.30.108.1.dynamic.telecom.kz (147.30.108.1)  8.320 ms  8.322 ms  8.308 ms
 3  * * *
 4  * * *
...
29  * * *
30  * * *

I'm located in Kazakhstan right now. I don't have any other network issues.