Of the players who left United U23s on a free transfer last summer, Matthew Olosunde appears to be doing the best. 20 starts in League One, 3 assists for Rotherham, who are currently 3rd in the table, though have played a game more than some of the sides just below them.
Regan Poole - regular starter for struggling MK Dons in League One. 13 starts, of which 11 as a CB.
DJ Buffonge - 3 sub appearances for Spezia Calcio in Serie B. Unused sub in most games
Matty Willock - one start for Gillingham in League One. It seems that a knee injury has kept him out for an extended spell.
Josh Bohui - 2 sub appearances for NAC Breda in the Netherlands 2nd tier Keuken Kampioen Divisie. A knee injury kept him out until mid November
Tyrell Warren - joined Salford City but yet to play for them
Callum Whelan - Watford U23s
Callum Gribbin - Sheff United U23s
Tom Sang - Cardiff U23s
Zak Dearnley - can't find any info apart from he was going for a trial at Rotherham in late August but got injured a few days before.
Other players to have departed recently for a minimal fee:
Nishan Burkart - 1 goal in 9 starts for Freiburg II in Regionalliga Sudwest
Lee O'Connor - joined Celtic but yet to appear for their first team
Ro-Shaun Williams - regular starter for Shrewsbury in League One
Going back to the United U23s team that got relegated:
Indy Boonen - KV Oostende in Belgian Jupiler Pro League. 1 start 9 sub. Often unused sub. Fewer mins than this time last season.
Tosin Kehinde - on loan at Randers in Danish Superligaen, from Feirense U23 in Portugal. 3 starts 4 sub. Mostly unused sub.
Joe Riley - joined Bradford, then in League One. Played a few games in August 2018. Out of favour after early managerial change. Bradford relegated. Suffered long term injury this pre-season.
Charlie Scott - played some non-league. Was at Altrincham briefly. Newcastle Town listed as his current club.
Devonte Redmond - fairly regular starter for Wrexham in the National League. Had a short spell at Salford City last spring as they won promotion from the National League.
James Wilson - 7 starts 4 sub for Aberdeen, contributing just one assist so far in the Scottish Premiership.
A few others that left in recent years:
James Weir - now at Bolton in League One, after his Hull contract ended. Was getting starts prior to the change of ownership, when team consisted mainly of youth team players. Unused sub in League One since mid September. Astonishing that Mike Phelan bought him for Hull when they were in the PL.
Will Keane - joined Ipswich after his Hull contract ended. Had spent last few months on loan at Ipswich. 2 goals in League One in 4 starts 6 sub.
Reece James - regular starter for Doncaster in League One, having left Sunderland.
Donald Love - mentioned in article posted previously, now a regular starter at Shrewsbury, having left Sunderland, where he was an occasional starter in PL, then Championship, then League One.
Joe Rothwell - just over 1000 mins in the Championship for Blackburn this season. Last season about 1500 mins in total. Joined Oxford in League One when he left United. Turns 25 in January.
Ashley Fletcher - scored 5 goals in 21 starts in the Championship this season for Middlesbrough.
Ben Pearson - regular starter for Preston in the Championship. Turns 25 in early Jan.
Tom Lawrence - now more famous for a car crash than his football achievements at Derby. Very fortunate still to have a career. 5 goals 10 yellow cards in 22 starts.
And some older ones:
Davide Petrucci - fairly regular starter for Ascoli in Serie B. His post United career path: Romania, Turkish Superleague then relegated to 2nd tier then promoted to Superleague, Italian Serie B.
Mats Moller Daehli - 1 goal and 7 assists in 15 starts for St Pauli in the Bundesliga 2. Been fit for the last couple of seasons.
Ryan Tunnicliffe - regular starter at relegation zone Luton in the Championship. His Fulham career consisted of 2 PL starts 1 sub then being sent on loan to various Championship teams.
Corry Evans - some starts, unused sub quite often for Blackburn in the Championship. Made over 200 starts in the Championship.
Kieran Lee - Steve Bruce generously gave him a contract for another year after a lengthy injury spell, before resigning to join Newcastle. Kieran has made 9 starts 6 sub for Sheff Wed this season.
Scott Wootton - playing for Plymouth in League Two after they got relegated. Was at MK Dons before that. Joined Leeds when he left United. Seemed a solid Championship player for a while.
Zeki Fryers - has been starting matches as a CB for Swindon, currently top of League Two. Until recently his career had been almost the out-field equivalent of 3rd choice keeper.