M1 Mac RAM and storage can be upgraded after purchase, but it's not easy - 9to5Mac
How to Upgrade RAM on MacBook Pro, iMac & More | AVG
How to Upgrade RAM on MacBook Pro, iMac & More | AVG
OWC 16GB (2x8GB) ram Upgrade PC3-12800 DDR3L 1600MHz sodimm 204 Pin CL11 Memory Upgrade Kit Compatible with Late iMac, Mac Mini, and MacBook Pro Computer at Amazon.com
How to upgrade the RAM on the new 2018 Mac mini | AppleInsider
A-Tech 16GB Kit (2x8GB) RAM for Apple MacBook Pro (Mid 2012), iMac (Late 2012, Early/Late 2013, Late 2014, Mid 2015), Mac Mini (Late 2012) | DDR3 1600MHz PC3-12800 SODIMM 204-Pin Memory Upgrade at Amazon.com