I'm just a guy who plays Minecraft, sometimes modded Minecraft on Java. Hopefully that's a fairly balanced overview of the situation.
There have been rumors that the Overwolf Linux client will come out before the old API is phased out, but I've yet to see a concrete release date. MultiMC's developer, u/peterix, while saying nothing officially, has stated on the MultiMC Discord that most likely " just remove altogether". There is no Linux support for the Overwolf Launcher, so most Linux players use third party launchers, primarily MultiMC, since it is so resource-efficient, although GDLauncher is also popular.
The Overwolf launcher (and FTB launcher, which uses the Overwolf launcher), is resource-intensive, requiring three applications to run in the background, which already stresses out systems that have trouble running Java Minecraft, which is already not optimized for running large numbers of mods on top of the Forge API. Other members of the community has responded more negatively, with members expressing concern on the following aspects:
Overwolf/CurseForge has paid out mod developers more since they took over, between three to ten times more, by some estimates, so it's not as if the money only goes to Overwolf/Curseforge especially since third-party launchers tend to bypass the advertising around Overwolf/Curseforge's ecosystem Overwolf/CurseForge is a business and are not obligated to provide access to third-party launchers. Reactions have been mixed, with established mod makers expressing support, pointing out that: CurseForge, in their November update, has announced that they decided to discontinue the old API with a new API that requires 3rd party launchers to request for API keys, allow mod makers to either allow or disallow 3rd party launchers to download their mods, and by default opt out new mods from being accessed by 3rd party launchers