Currently use the Mantiz Venus. Thinking about an upgrade to RDNA 2 (also expecting native macOS support for it sometime soon).
The Asus Liquid Cooled cards might be nice. But in which eGPU cases would they fit nicely?
Late 2016 15" MBP w/ Radeon Pro 460, 2m CalDigit TB3 cable, Mantiz Venus eGPU case, NVidia GTX 1080ti.
@reinhard1004, There's no eGPU enclosure that would accommodate the 240mm radiator. Your Mantiz Venus may serve as a good frame to create a custom mount. You can remove the left side panel (PSU side) then figure out a way to mount the radiator. Another really good enclosure to use is ASUS XG Pro. It has two 120mm fans behind the GPU so you can mount the 240mm radiator once the panel is removed. The disadvantage is no Power Delivery.
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• external graphics card builds
• best laptops for external GPU
• eGPU enclosure buyer's guide
2020 13" MacBook Pro [10th,4C,G] + RX 6700 XT @ 32Gbps-TB3 (CM MasterCase EG200) + Win10 1903 [build link]
@reinhard1004, have you found a solution to this? Facing the same issue / question...
To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.
.@reinhard1004, have you found a solution to this? Facing the same issue / question...
Not yet. Maybe it could be fitted into the Mantiz Venus with with a bit of drilling and cutting. But also don’t yet own a 6800/6900 card because it is not yet supported under macOS and the availability and prices are still quite bad.
Am still interested in potential solution for this though. 
Late 2016 15" MBP w/ Radeon Pro 460, 2m CalDigit TB3 cable, Mantiz Venus eGPU case, NVidia GTX 1080ti.
@reinhard1004, There are now drivers for Navi21 as of macOS 11.4 Beta. Prices are still not affordable and availability is even worse.
LinkedIn | Twitter | Facebook | Youtube | Instagram
• external graphics card builds
• best laptops for external GPU
• eGPU enclosure buyer's guide
2020 13" MacBook Pro [10th,4C,G] + RX 6700 XT @ 32Gbps-TB3 (CM MasterCase EG200) + Win10 1903 [build link]