There is a bug that doesn't let you open the quest panel when there's "Ancient Mana" or "Arcane Thirst" involved (quests like "Lingering on the Edge" or any quests from "Layline Bling" achievement in Broken Isles, Suramar)

You can accept these quests, but when you want to give the quest giver the Ancient Mana currency to complete it, the quest window doesn't show unless you have "auto turn-in quests" from another addon.

The Dragonflight NPC in Valdrakken, Therazal, offers you quests to choose which zone you want to aid. (Dragon Isles, Zaralek Caverns, Amirdrassil)

When pressing him, a window pops up with pictures and brief descriptions, with the buttons "Choose Quest."

These buttons do nothing, and the addon automatically shows the middle quest window (Zaralek Caverns) to accept.

My Nightfallen NPCs are currently stable, so I'll have to verify it tomorrow. Other quests that require currency to complete like exchanging Order Resources for bonus roll coins in Dalaran seem to work correctly.

Quest Last Hurrah has been bugged since 11.0.0
https://us.forums.blizzard.com/en/wow/t/therazal-weekly-quest-interface-bug/1900261/24
Stanzilla/WoWUIBugs#612

Just in case, I think the examples from Legion I mentioned are all easily accessible on Party Sync from the get-go without the necessity of completing any other quests before