Late April Day Trip from Luzern - Rail & Hike

Welcome to the forum gpereyra! If you want to return to Lucerne the same day, you're limited in terms of where you can hike. Graubünden, including Disentis, would be way too far off for a day trip. You can check traveling times here. The Muotathal trail or the Bernese Oberland would be a more obvious choice. By the end of April, many of the high altitude tracks are still covered by snow and thus inaccessible, meaning you'll have to search for hikes at lower altitude 0I'd say under 2000 metres above sea level), unless you're a very experienced hiker with proper winter gear. Make sure you inquire about weather and hiking trail circumstances at a local tourist office before taking off. Whichever route you pick, you don't have to worry about 'touristy' routes as you're traveling outside of the tourist high season.

Now, as for options: I think you're referring to a section of the so-called Suworow-trail when mentioning the Muotathal-Altdorf trail. The route gets up as high as 2700 metres, which is too high for the end of April. This section of the same route might be more suitable. Consider some lower sections of the Via Alpina in the Bernese Oberland as well, such as Meiringen-Grindelwald or Grindelwald-Lauterbrunnen via Kleine Scheidegg (probably still covered in snow). In clear weather, spectacular views are guaranteed. The train ride from Lucerne is great too: pick the Golden Pass route via the Brünig Pass and Meiringen.

I hope this helps you choose a route!