Well, COVID-19 effectively put an ice age on the entertainment industry, so, it's possible it's still being worked on, but it's on such a back burner as to be frozen.
The Facts are, well, the initial announcements were made. Since then, every couple of months a cast member will be asked about it, say they haven't heard anything, but would be happy to make a cameo or guest star, usually. On occasion, a ragsheet internet publication will publish some sort of unfounded fan theory passing as news. Like Black Slayer will really be Dawn, who just found Superman's Race Changing machine used in Superman's Girlfriend Lois Lane #106. (Ed. I know, I promised this would be the facts section, but I have to discuss sources) Or that the Comics are a rebuild of Buffy series designed to rework the series without the "problematic" elements, like Xander being a male, or Xander being white, or Xander not understanding that he's actually gay, or Xander not being killed by Vampires, you know, the type of thing that loses the kids. (Ed. Although, to be fair, the only Boom! Comic that still has any defenders is Willow. Although, i kind of wish it was called Buffy's Best Friend Who is Recently Gay, Willow; I Fight With Weapons.) So, basically, no creditable third party sources have said anything on the matter.
There have been no PR announcements, no announcement of network, financing or production company, or casting, the things you would associate with active pre-production. Variety, the Hollywood Newspaper of Record, has not published any information on the matter since July 26th, 2018. While it's possible it's really under the radar. The Showrunner's Twitter Posts mostly deal with old work and with politics. There is no reference to Buffy in her "About Me" section.
My opinion: This, like the Boom! Comic Line, was done to inflate the value of 20th Century Fox Properties during the Merger & Acquisition Audit. Instead of Buffy appearing in terms of just DVD sales, streaming fees and licensing agreement, it was now an active license with new and potential deals. The actual roadblock is a licensing issue. To Use Buffy, you have to pay off the Film Producers, you have to payoff Mutant Enemy, and you have to payoff the Television show producers, whereas, a Girl power YA Book production license is much cheaper to acquire, and doesn't come with baggage of a very emotionally invested and thus potentially very toxic fandom.
So, I'm inclined to say that production is currently dormant, and will maintain that stance until Monica Owusu Breen announces another job or some sort of announcement about pre-production is made. The former would persuade me that it's been canceled, the latter will persuade it it's back on. I could be wrong, but 30 months without anything is an awfully long time in Hollywood.
