There is modpacks but they are only mostly advertised in the Fabric Discord and used with the MultiMC launcher far so for testing (besides I guess All of Fabric), I don't know much about user modpacks but for the one I had witnessed it was rejected from curseforge due to their 'Twitch automated download' requirements or something which makes sense as Fabric isn't supported through the Twitch Launcher yet (even though you can do that but not export modpacks just get the game working with Fabric 'Unofficially', I found that out pretty easily really with the right files similar to who you would setup Fabric with Vanilla with only the folder location being the only difference XD, but anyways), but to my knowledge most or all come from the Fabric devs besides my own and are only possible through MultiMC. Sure you can use MCUpdater or Technic if your a mudpack dev but I'm not sure about these myself, their development or any publicly published packs. At least not on Technic there isn't any.
While a request for other modloader support has a fair amount of votes for Twitch support, it's not made much difference really even though I'd like it be possible to due to the traffic it has and the want for 1.14 modpacks. I plan to advertise Fabric stuff and maybe some 1.14 modpacks on a Fabric/1.14 Mods Discussion thread as a 2.0 of sorts due to the MCForums archiving and me needing a new place to put modpacks, mod links, mod updates/new mod releases, with 1.14 mod help (as in users asking questions and me helping to answer them besides recommending the Fabric devs if I'm unable to and it's a major conflict) and tutorials over just some Discord or Reddit or other places that don't really suit.
So if your after 1.14 modpacks or a way to create your own I know just where to look but I have to get started on this new thread over this week from what I'm archiving from the MCForums to port that over to here. At least that's my goal
Otherwise though I'd love to see Fabric come to the FTB launcher or Twitch Officially besides just Vanilla, MultiMC, MCUpdater and I think Technic has been newly added at least but I haven't learned how to set it up yet.