So, Phonomorph (my sound change program) is ready for some serious
alpha-testing, although the GUI is still a distant dream, and the whole
damn purpose was (originally) to demonstrate GUI programming for a college

I'm looking for in-depth charts of sound changes between any two
languages, and substantial fully-pointed texts in any of the source

I have Beekes, so I can make a start doing several PIE -> X change lists,
but I lack for source texts. Quasilikewise, I have found many Latin texts
(even a few with vowel length marked), but no good lists of sounds changes.

For your entertainment, here is a certain sentence(*) after running it
through my test changes...

NekŲ porro kŁskw„ est, kŁ dolore ipsu kuya dolor sit amet, kontsektedur,
azibissi welit, sed kuya non numkw„ eyu mozi tempora intsizunt ut lawore
et dolore magn„ alikw„ kwaerat woluptade.

As you will no doubt be able to tell, more work is definitely required,
but it's a start.

(*)Those who untranslate it ought to be able to discern why I felt it