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Apple sells two version of a "Multiport adapter" with a USB port, a Thunderbolt 3/4 port (to make up for the one being used by the adapter), and either a HDMI or VGA port.
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USB-C Digital AV Multiport Adapter f
USB C to Mini DisplayPort Adapter
Apple has not yet released a Thunderbolt 2 to Thunderbolt 3/4 adapter yet, but StarTech has. This will save you from having to buy all new adapters if you already have Thunderbolt 2 adapters and your new computer comes with Thunderbolt 3/4 ports
Apple sells a Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter.
StarTech.com USB C to Mini DisplayPort Adapter is another excellent option: Mfg. Part#: CDP2MDP (in UC procurement in the CDWG punchout it is labled USB C to Mini DP - 4K 60Hz with part number CDW #: 4888589 )
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