Apologies if they've already been mentioned (I couldn't find them, at least!): Leonel Sánchez - LM/LW for Colo Colo & Chile NT. Jean Beausejour - LB/LWB/LM for Colo Colo, Wigan Athletic & Chile NT.
Four former Coventry City players: Kenny Sansom - LB who also played for Crystal Palace, Arsenal, Newcastle & the England NT; Terry Butcher - CB who also played for Ipswich Town, Rangers & the England NT; Steve Staunton - LB/CB/DM - also Liverpool, Aston Villa & Ireland NT. Robert Jarni - LB/LWB/LW - who was technically a Coventry City player...for approximately a day, before he was sold to Real Madrid (the rumour being that Real Betis wouldn't sell to Real directly and so...yeah, some shenanigans occurred )
Two from Independiente: Ricardo Pavoni - LB (also Uruguay NT); Raimundo Orsi - Winger. I'm slightly unsure on the second of these, but I believe Orsi to've been a left footed winger (who played both for Argentina & Italy) who also played, at least some of the time, on the right wing - which would have been very unusual for the era (1930s). Anyone?
A handful of Middlesbrough alumni: Terry Cooper - LB - also of Leeds & England NT (may have been mentioned elsewhere, but not sure); George Hardwick - LB - not 100% sure, but he's certainly shown kicking a ball with his left foot in the statue outside the Riverside (as well as being a left back). Andy Townsend - CM - also of Aston Villa & Ireland NT; Christian Ziege - LB/LM - also Borussia Moenchengladbach, Liverpool, Tottenham & Germany NT
Three from Forest that I don't think have been mentioned: Archie Gemmill - CM - also Derby County & Scotland NT; Jim Baxter - left half - played briefly (and unsuccessfully) for Forest but beautifully for Rangers & the Scotland NT; Des Walker - SW/CB (also Sheffield Wednesday, Sampdoria & England NT) - a controversial one, this, as he appeared on the right side of the central defensive three at Italia '90 - although that three also featured Terry Butcher (very left footed), on the left and Mark Wright at sweeper. Certainly tackled and passed very well [although very economically. He was certainly no Koeman/van Dijk with the ball!) with both feet. I just have a feeling he slightly favoured his left - which was, if memory serves, the foot that he used to bulge the net on his first ever goal (which came several hundred appearances in to his career). Might need our resident Forest expert for this one!
A couple from Partizan Belgrade: Branko Zebec - one of the greatest utility players of all; played left wing, centre-half and, I believe, at left back among other positions. Very unusual for the era. Savo Milošević - CF - also of Aston Villa.
Oscar Más - LW (and occasional centre-forward) for Quilmes, Argentina and, most famously, River Plate.
Some candidates from Glasgow Rangers - only the first of which I'm sure of , so happy to be corrected! Frank de Boer - LB/CB - more famously, though, for Ajax & Barcelona (as well as Galatasaray and others); Alex Smith - LW; Alan Morton - LW
'Kily' González - LM/AM - numerous clubs, including Boca Juniors, Valencia, Real Valladolid & Argentina NT.
A couple from Vélez Sarsfield: Norberto Alonso - CM/AM - better known, though, from his time with River Plate. Luis de la Fuente - footage I've seen is somewhat inconclusive, and he seems to have been pretty comfortable with both feet, but slightly stronger with his left.
A trio of ex-FC Basel players all now plying their trades in England: Mo Salah - F - also formerly of Chelsea and Roma, now of Liverpool; Xerdan Shaqiri - M/WM - ex-Bayern Munich & Stoke City; now of Liverpool; Granit Xhaka - DM/CM - now of Arsenal.
A few Brazilians that I don't think have appeared: Amarildo - ST - Botafogo, Milan, Fiorentina (among others) & Brazil NT; Jonas Eduardo Américo (aka Edu) LW - Corinthians, Santos & Brazil NT; Mario Zagallo - LW/ST - Flamengo & Brazil NT; Zinho - AM/LW - Flamengo, Miami Sharks etc & Brazil NT; Jair da Rosa Pinto - LW - Santos & Brazil NT Canhoteiro - LW - Sao Paulo & Brazil NT Tostao - AM/ST - Vasco da Gama & Brazil NT
Bruno Bellone French left winger who played for Monaco, Cannes and Montpellier between 1980 and 1990.
John Lauridsen Danish international midfielder who played for Esbjerg, Espanyol and Malaga from 1978 to 1992.
Raymond Dubly, left winger of RC Roubaix 1913-1925 (Uckfield FC, England, as a junior according to his wiki page. Born in Roubaix). 31 French NT caps, 4 goals, 13 assists (source for the assists : FFF site, the description of the goals). He formed a remarkable pair of wingers with Jules Devaquez. Dubly was first of all an assist-man while Devaquez was the artist able to score goals. In this article, he says that he trained in the English fashion, what could correlate with the fact that he spent some time in England as a young footballer. It also says that Devaquez could shoot hard with both feet.