I don't know, but Chinook has been unbeatable for all intents and purposes since about 1994; and AFAIK, while it was running on a powerful computer for that time, it wasn't even a purpose-built supercomputer such as Deep Blue.
Draughts / Checkers have limited opening theory compared to chess.
Massive opening books and table bases (even compared to chess) exist, but I don't know if there are any for free. I assume so.
The rules are simpler than those of chess, and there are many positions with only one legal move: if you _can_ capture, you _must_ capture, and if there are multiple capture possibilities, the one capturing the most pieces _must_ be played.
As there are very large opening books and table bases, the computer only has to survive a relatively short, super-tactical middle game, which is right up its alley. IMHO, for all practical purposes, checkers / draughts is solved. You play it because you want to, not because there's ever a chance you could beat a computer at it.
Heck, even chess is "solved". Following GothamChess on YouTube, I see him, as a 2350 player, make opening preparations up to 20 moves and getting frazzled if the opponent plays something he didn't prepare for. Sometimes he says "this position is practically lost", and he's just at move 21. Also he sometimes says: "This position has been reached many times before...." (At move 30+...)
There are table bases of up to 7 pieces now. So even in chess, the computer has to only survive a relatively short middle game, so even chess is "solved" for practical purposes... but the one thing we can still learn from computers is that (opening) positions that were deemed unplayable actually ARE playable.
I see GothamChess play openings that were ... not a thing ... when I learned to play chess in the 80's. If I'd had a teacher back then and I would play some of the current-day openings, he'd be swiping the pieces off the board because of "idiotic play"... but today, computers have proven these lines to be perfectly playable, and now they're theory. Since I've been writing my chess engine I've also started to play chess more, against weaker engines (sub-2000 CCRL Elo), and I _really_ have to update my opening repertoire when I make opening books from games played after 2010. If I make opening books from games played after 2015-2016, I'm in danger of getting my eyes crossed... permanently. Some of that stuff is unreal to someone who has been playing chess only intermittently in the last 20 years (with a max rating up to 2000 Elo, around the year 2000).
