\noindent
We are grateful to Giulia Zanderighi for giving us the opportunity to
write this Report.
%
We are also indebted to many colleagues for extensive discussions and fruitful collaborations of the topic
of PDF determinations in the last years.
%
A necessarily incomplete list of colleagues that we would like to thank for this includes
Alberto Accardi,
Sergei Alekhin,
Richard D. Ball,
Josh Bendavid,
Valerio Bertone,
Marco Bonvini,
Ulla Blumenschein,
Stefano Carrazza,
Mandy Cooper-Sarkar,
David D'Enterria,
Sayipjamal Dulat,
Stephen Farry,
Stefano Forte,
Rikkert Frederix,
Stefano Frixione,
Marco Guzzi,
Nathan P. Hartland,
Tie-Jiun Hou,
Joey Huston,
Zahari Kassabov,
Valery Khoze,
Jan Kretzschmar,
Rhorry Gauld,
Sasha Glazov,
Joey Huston,
Katerina Lipka,
Jon Pumplin,
Michelangelo Mangano,
Alan Martin,
Simone Marzani,
Ronan McNulty,
Alexander Mitov,
Pavel Nadolsky,
Emanuele R. Nocera,
Luca Perrozzi,
Ringaile Placakyte,
Klaus Rabbertz,
Voica Radescu,
Misha Ryskin,
Albert de Roeck,
Luca Rottoli,
Robert Thorne,
Gavin Salam,
Carl Schmidt,
Peter Skands,
Daniel Stump,
Maria Ubiali, and
C.~P. Yuan,
among many other colleagues that have helped
pushing the boundaries of global PDF fits to a level that would have
seemed impossible just a few years ago.\\[0.3cm]


\noindent
J.~R. is supported by the European Research Council (ERC)
Starting Grant ``PDF4BSM'' and
by the Dutch Organization for Scientific Research (NWO).
%
The work of J. G. is
sponsored by Shanghai Pujiang Program.
%
L.~H.~L thanks the Science and Technology Facilities Council (STFC) for support via grant award ST/L000377/1
{\tt add all funding ID}.


