"new" Mac Mini + 2 "OLD" Thunderbolt Displays

The specs for the 2018 Mini

Support for the following combination of maximum concurrent display setups:

• Up to three displays:
• Two displays with 4096-by-2304 resolution at 60Hz connected via Thunderbolt 3 plus one display with 4096-by-2160 resolution at 60Hz connected via HDMI 2.0
• or
• Up to two displays:
• One display with 5120-by-2880 resolution at 60Hz connected via Thunderbolt 3 plus one display with 4096-by-2160 resolution at 60Hz connected via HDMI 2.0

Thunderbolt 3 digital video output supports

• Native DisplayPort output over USB-C
• Thunderbolt 2, DVI, and VGA output supported using adapters (sold separately)

Based on the following two Apple Thunderbolt display daisy chained from one USBC port via a Thunderbolt 2>Thunderbolt 2 adapter should work

https://forums.appleinsider.com/discussion/207904/connecting-two-apple-thunderbolt-displays-to-macbook-pro

Based on the specs the free Thunderbolt 3 via adopter will likely not support another TB display.