Ground Cover For Low PH Tank

Low tech carpet plants are something I get asked about all the time... there are two species that are almost bullet-proof. I have them both growing in sand (so nothing special) and have grown them without fertilizing the water column too...

Dwarf Sag is like mini vallis looks wise and grows quite fast spreading via runners. It's reasonably tall so far as carpetting plants (up to about 7 or 8 cm) go but will grow more compact with better lighting. I personally have found it to grow more compact under harsher conditions too.
https://tropica.com/en/plants/plantdetails/Sagittariasubulata(079)/4530

Lilaeopsis grows a bit more compact (3 to 4 cm) and is a more traditional looking carpet. It is proper hardy... can be grown in ponds! A lift more slow growing but my personal favourite for Shaw. Like an easier version of hairgrass.
https://tropica.com/en/plants/plantdetails/Lilaeopsisbrasiliensis(040)/4459

If you have a look on the tropica sites there are other low tech carpetting plants listed there too and I have tried nearly all of them out so if you really want to ask about a specific type let me know.  The 2 above are the best ones in my experience though...

Here's a filtered list of easy foreground plants on Tropica's site...
https://tropica.com/en/plants/search/?mode=search&sew=&dif=Easy&pgr=&ori=&use=Forgrund

I wouldn't worry too much about your pH... you'll see for example tropica don't provide this detail for their plants... with plants I do find you might have to try a couple of species to hit on something that works in your tank, but there's no easy link to pH, hardness etc etc, that can be reliably formed...