My apologies, I thought I saw some links provided before.
I did receive two responses to a support request from one of the support staff at Blackview through the support page, though, perhaps they will be of use. It's older than current, but I used it early on and still was able to receive OTAs afterward so I trust it's as official as one can get without it being posted right on the main homepage.
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[td]2018-11-26 08:15:38
Re:PTT Software[/td]
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[tr][td][/td]
[td]They have released a new software to solve your problem,
please update your phone to the newest version via the below link:
https://mega.nz/#!cxMCmCTb!nqLWU9DnRMUY ... UfZcR1sPJE[/td]
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[table][tr][td][/td]
[td]2018-12-03 10:36:04
Re:PTT Software[/td]
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[tr][td][/td]
[td]This is the newest link they sent me,please be note.
https://mega.nz/#!cxMCmCTb!nqLWU9DnRMUY ... UfZcR1sPJE[/td]
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Of course, they're the same link. If memory serves, they're the August 2018 revision, and they're for the PRO, not the non-pro. They're in RAR format, and whoever uses them will need to know what they're doing (and with that I can't help as I've only done it successfully once and it was nearly six months ago). Hopefully these are useful.