I think that's why Linda's return should go the Red Hood route, bring her back initially as a villain and enemy of the Superfam, people not in know will hopefully be fascinated by this new mystery forgotten Supergirl is who apparently has history with Clark and the others but who they don't remember and wonder what's the deal with her weird fire powers. Linda's initial story was all about she had done a lot of bad things in her past so the idea that she fell back into that dark place after losing everyone and having her whole existence erased due various cosmic reboots is understandable and makes her a sympathetic villain with a personal ties to the Superfam while offering her the chance to have a redemption arc down the line.
I know everyone wants to just have her come back and more or less pick up from where she left off with a new codename and be a hero again but realistically if you want to effectively sell her to todays audience who have no idea who she is then similar to how Jason and Bucky where brought back after decades she needs to be reinvented significantly, maybe not the dark anti-hero route (though I think it could work) but definitely something that'll make splash and grab people's attention not just the few dozen Linda fans who still exist.