None of the options appear to apply any filtering and none of the custom expressions work either.

Looks like they come from https://wow.tools/dbc/?dbc=mapchallengemode&build=10.0.0.44895#page=1

It is missing the activity ids for the new dungeons. https://github.com/0xbs/premade-groups-filter/blob/master/Modules/PlayerInfo.lua#L32

I am trying to figure out where those activity ids come from

You will need to update World of Warcraft\_retail_\Interface\AddOns\PremadeGroupsFilter\Modules\PlayerInfo.lua line 32-42 with

C.CHALLENGEMODE_MAP_ID_TO_ACTIVITY_ID = {
    [375] = 703,  -- Mists of Tirna Scithe
    [376] = 713,  -- The Necrotic Wake
    [377] = 695,  -- De Other Side
    [378] = 699,  -- Halls of Atonement
    [379] = 691,  -- Plaguefall
    [380] = 705,  -- Sanguine Depths
    [381] = 709,  -- Spires of Ascension
    [382] = 717,  -- Theater of Pain
    [391] = 1016, -- Tazavesh: Streets of Wonder
    [392] = 1017, -- Tazavesh: So'leah's Gambit
    [169] = 1195, -- Iron Docks
    [370] = 2097, -- Mechagon Workshop
    [369] = 2097, -- Mechagon Junkyard
    [166] = 1208, -- Grimrail Depot
    [234] = 1651, -- Return to Karazhan Upper
    [227] = 1651, -- Return to Karazhan Lower
}

the comments say where its from:

/run for _,mapID in pairs(C_ChallengeMode.GetMapTable()) do local name = C_ChallengeMode.GetMapUIInfo(mapID); print(mapID..","..name) end

Ive updated my copy with the new values. good find

Please consider opening a pull request in the future :)
Latest version includes updates.

I would have normally opened a PR but I didn't want to have to clone it all, setup my stuff and create the PR 🤷‍♀️