KRPP vs KRP - maximum depth to conversion? I am trying to learn single rook endgames with two pawns against one, with added stipulation that the two pawns of the attacking side are on neighboring files with the pawn of the defending side also on one of those files. It could for instance be e+f pawns vs f pawn or g+h pawns vs g pawn.

What is the most complicated such position that is still won for the attacking side? To make the question precise, I am asking for the position with the maximum depth to conversion.
As Glorfindel notes,
the Lomonosov tables are great but might not have the answer you want.
In RPP/RP, according to the list in
this
article by Guy Haworth, we find that the maximal distance to mate
is 200+ moves, from the following position -- which happens not to have
the White pawns connected, but worse for your purpose,
it looks like most of the play is post-conversion:

[Title "Black to move; White eventually wins"]
[Fen "8/k1P5/8/8/1R5P/7p/r7/1K6 b - - 0 1"]
[StartFlipped "0"]

1...h2 2.Kxa2 h1=Q 3.c8=R!


after Kxa2 we're in 6-man territory, and the k4it.de site says
"Win in 216" starting Qd5+ 4 Kb1 Qa5(d6) -- that's right, not Qd1(h1)+,
which lets White win in only 200, nor Qd3+, which hastens the end
by another move (199).

Possibly Guy Haworth has enough access to 7-man tables
to get the answer to your query.