Hiya! Currently 0xacab is limited to riseup.net account signups, so I can't post an issue to the real bug tracker. In short, Calyx has silently ended support for Bitmask as a VPN provider, and it's still made available as of the most current release on the Play Store and Fdroid.
Calyx has taken the time to remove references to it - for the most part - from their site, and all attempts to set up the Calyx provider result in an error that Calyx doesn't look like a Bitmask provider. That would, to my knowledge, leave Riseup Networks as the only available Bitmask provider for use.