[Galaxy S 5 General] John Bentley:
With thanks to [MENTION=1332871]prodigiez[/MENTION] the original post currently specifies that the following Android system mods are available to Samsung Galaxy S5 SM-G906[K|L|S] users:

Root: "Unofficial CFroot".

Custom Recovery: "Unofficial PhilZ recovery", with a link download to unofficial_philz_touch_6.48.4-g906s_hsk.tar

Custom ROM (also known as "Firmware"): miscom's [ROM] [G906S/K] Korean S5. prodigiez currently specifies this as "BASED ON G906KKTU1ANH2".

Are their alternatives, proven or plausible, for SM-G906[K|L|S] users?

By an "proven alternative" I mean: there exists linkable evidence that the alternative works on a SM-G906[K|L|S].

By a "plausible alternative" I mean: there is no known reason why the alternative shouldn't work with a SM-G906[K|L|S], perhaps with some adaptations, but it hasn't yet been experimentally verified by on a SM-G906[K|L|S].

By asking for proven alternatives or plausible alternatives I don't mean to necessarily cast aspirtitons on the current mods, my thanks goes to those that have done work on them . Rather, I want to get clear on the current range of options. And, of course, there are some limitations with the mods listed in the original post (e.g. tripping knox, factory reset problems) that may not exist in an alternative.

So, specifically, are the following alternatives, proven or plausible, for SM-G906[K|L|S] devices?

ROOT

Towelroot (possibly with "modstrings"). [TUT] root WITHOUT tripping knox.

Towelroot with old kernel toggle. [How to] Root without triggering KNOX? 2nd Method, works for Fimware ANG2 and above. This is supposed to work on some Galaxy S5 variants that have later firmware unable to be Towelrooted using the first (above) method.

CUSTOM RECOVERY

In the original post, SM-G906S/K/L/ S805 Info Sharing thread (Root/CWM/Custom Rom) the "Unofficial PhilZ recovery", links to unofficial_philz_touch_6.48.4-g906s_hsk.tar.

Latest version of [klte][CWM Advanced Edition] PhilZ Touch. Are the files philz_touch_6.57.8-klte.* linked to from [klte][CWM Advanced Edition] PhilZ Touch those that we ought now use? What does "klte" stand for ("Korean LTE phones", a reference to SM-G906[K|L|S] phones?)? If so, does this latest Official Philz Touch Recovery solve the factory reset bug that we are warned about in the OP?

TeamWin Recovery Project (TWRP). TWRP 2.8 - Samsung Galaxy S5 page.

Unofficial ClockwordMod Recovery (CWM). [RECOVERY][UNOFFICIAL] CWM Recovery for the Samsung Galaxy S5.

FIRMWARE/ROM

A Samsung stock ROM from sammobile. For example, the history of samsung stock roms for the SM-906K, with instructions as for the SM-G906K. The title of this thread specifies "Custom Rom" but could someone confirm that installing Samsung stock Rom from sammobile, following the sammobile instructions, works for a SM-G906[K|L|S]?

Original Post needing to update or remove miscom version information? In the original post [MENTION=1332871]prodigiez[/MENTION] links to miscom's [ROM] [G906S/K] Korean S5. prodigiez writes that this "ROM BASED ON G906KKTU1ANH2". However, miscom, these days, specifies "G906K BASED ON G906KKTU1ANH6" and "G906S BASED ON G906SKSU1ANH5". Perhaps prodigiez need to update the original post to update the version information or (probably the better move) remove version information (so that miscom's post can be updated without causing this inconsistency).

Edit 01: Corrected list markup error (where a list item would not appear) to make second Towelroot candidate alternative appear.

Edit 02: Added "of".