All Thunderbolt which works through a USB-C type port is Tbolt 3:
This from your Manual:
15-bl100 – 15-bl199, 15t-bl100 15-bl000 – 15-bl099, 15t-bl000 USB 3.1 Gen 1 port USB 3.0 Type-C ports USB 3.1 Gen 2 port with Thunderbolt™ Gen 3 technology USB 3.1 Gen 1 port All ports support data transfer, power delivery, and: DisplayPort 1.2 supporting up to 3840×2160 @ 60 Hz HDMI v2.0 output support up to 3840×2160 at 60 Hz with HDCP 2.2
Yours is Thunderbolt 3 and will support an eGPU.
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