Does anyone think Devon ditched Maul on Malachor?
It could absolutely not be the case, but Maul's training took him to Malachor a few times and when he shows up in Rebels, he says he hasn't spoken to anyone in years and he pretty aggressively tries to recruit Ezra as his new apprentice.
It makes me wonder if maybe Devon left him there upon (presumably) finding out about Daki. Him being stranded implies his way to the planet was cut off, and he kills 2/3 Inquisitors that he encounters there pretty easily so it's hard to believe they were keeping him there in any capacity. Presumably he could've just killed the one who's after him (the Tenth Brother I think?) and taken his ship to go try to recruit somebody to open the temple on Malachor, instead of waiting literal years for anybody to happen upon him and getting lucky that the person who did eventually happen upon him is both willing and able to help him.
So given all that, he presumably can't get off the planet until the Inquisitor(s) show up, which means he was somehow stranded there and has not been there entirely deliberately. It seems like he would trust her a lot, as he already seems to (and seemed to trust his previous apprentice a lot), especially given that he would have longer with Devon than he did with Savage by far. So, if he trusts her a lot, then he would be more vulnerable to being betrayed by her. Plus, he talks a whole lot on Malachor about how there are always 2 Sith, invoking the Rule of Two a whole lot. The Rule of Two also always results in the apprentice beating the master (if the master wins, they find another apprentice until eventually they are in theory killed by the apprentice), but Maul's death is already written, so perhaps she beats him here as a completion of her apprenticeship. Maul isn't a Sith anymore, but he was raised as one and believes much of what they teach, but not all of it, so it's possible he still saw this as a way to teach, but it could just be good writing that he's defeated in what is effectively a Sith ritual. It would also definitely explain why he's alone at a temple he quite possibly knew required 2 to activate and even enter.
It would be a good way to tie up Devon and Maul's interconnected story while letting her continue after, and Maul obviously also continued after for some time. It would mean that Maul quite possibly teaches Devon using some methods he was taught with, which would also narratively explain why Devon hasn't shown up in other stories, because Maul was a shadowy agent of Sidious, and so he would quite possibly have her learn by going off and doing her own thing pretty regularly. It would explain why Maul seems to have not gone looking for Devon when he's back off Malachor, because he may quite possibly have just accepted her leaving on some level. He hates Sidious for what he did to Savage (and other reasons), so he may well understand Devon hating him for essentially killing Daki. He already obviously understands that concept enough to keep it a secret from her.
So, what do you all think? I know this is speculation that could totally be wrong, but I think it would be cool! It would be really ominous any time they go to Malachor if you think she's gonna find out about Daki on that planet. It explains lots about each character separately and together. I'm happy to be wrong but I'd be happy to be right too. Honestly I'm pretty confident this show will be done properly regardless, so this is just fun speculation.