The no tech tank is already in process! I'm dry starting a hairgrass carpet and it'll be a bit before I flood it. I should really start a journal for it.
I have to ask about your undergravel filter though! What kind of substrate do you use? How do you manage it so your plant roots don't clog it up? I've read that running a reverse flow undergravel filter prevents this from happening, but that wouldn't allow the mulm to settle. Whatever I read didn't have me convinced, so I'm running a HOB now. It's ok. It works, but the flow isn't as even, it's ugly, and I occasionally have to service it. I have fond memories of my UGF in my fish-only tank of yore.
I actually run UGFs on all my tanks. I saw profound improvements on my tanks when I put them on in terms of water clarity and root health. The only tanks I don't run UGFs on are sand tanks (by sand I mean really fine, think pool filter sand). I don't run any sand tanks anymore because I don't like the compaction and I think they are bad for plants. I also run pretty thick substrate layers, 2 inches at the lowest and with this thick substrate I have never had roots clog it. Some people don't like the look of the thick substrate layers which I get but I think all plants, UGF or not, benefit from a thick substrate. They have gotten hair structures down in there occasionally but it has never caused issues for me. I am also currently testing dirted planters which allow me a bit more flexibility with my soil types while running UGFs. You can see my initial tests in my tank journal.
Currently I have UGFs in all of the following substrates:
Quartz coarse gravel
Quartz fine gravel (think coarse sand)
Samurai Soil (buffering clay based aquasoil)
It is also worth noting that I don't think they would work well with aqua soils that break down over time (I've heard this can happen with Brightwell and others). I also wouldn't run it with dirt (duh). I also have never tried it with the coated soils like ADA substrate and I think a purist would consider it blasphemy to run UGF on an ADA style tank LOL.
To clean an undergravel filter system, I just hook a wet-dry vac up to the lift tube (like a shop-vac). Takes two minutes and it sucks all the crud out that settles on the bottom. I do this at the same interval I clean the rest of my filters. That being said, I have had people ask before about the dust that will inevitably work its way down through the gravel. IME I have seen this come straight back through the lift tube and "rain" back down on the surface and start the whole process over. I use the "dust" sprinkling around the lift tube as an indicator that it is time to pull out the shop-vac and clean my filters.
If you are doing dry start I assume you're also using aquasoil so I would check that your aquasoil isn't prone to breaking down. I usually just check mine by taking pieces that have been soaking and squishing them between my fingers. If they break up, probably not the best option for UGFs.
I hope all this helps. It has worked for me