Armstrong signed a deal with the Cowboys, Todd Archer of ESPN.com reports.
Armstrong was released by the Saints on Tuesday, Amie Just of The New Orleans Times-Picayune reports.
Armstrong signed a contract with the Saints on Wednesday, Mike Triplett of ESPN.com reports.
Armstrong signed a contract with the Browns on Thursday.
Armstrong has been ruled out for the remainder of Thursday's game against the Eagles due to a concussion, Ralph Vacchiano of SNY.tv reports.
Armstrong made 10 tackles (five solo) and forced one fumble in five games with the Giants during the 2017 regular season.
Armstrong was claimed off waivers by the Giants on Monday, Ian Rapoport of NFL Network reports.
Armstrong recorded five tackles (all solo) in Sunday's blowout loss to the Cowboys, but he was only on the field for 27 of the team's 75 defensive snaps.
Armstrong (shoulder) is listed as active Sunday against the Cowboys
Armstrong (shoulder) is listed as questionable for Sunday's game against the Cowboys, Nick Wagoner of ESPN.com reports.