I'm a newbie here. I bought a Akito Node, TB3 eGPU for my late 2015 27" iMac. The OS sees the enclosure but when booted up with the EFI USB flash drive, no eGPU was detected. The MacOS is Catalina, 10.15.6.
I'm not sure where to begin trouble shooting. My objective is to improve the performance of X-Plane flight simulator.
Hey @kenka433,
While I'm not familiar with booting from a EFI USB Flash Drive, I'm going to guess what's missing here is purge-wrangler install...? Others may be able to answer more specifically... with the iMac having an integrated screen I have a feeling there may be other points to check as well - might be helpful to have a look through the 'software' tab at the top of this site.
I'd think the RX580 should help - I recently tried an eGPU + RX580 and it made a huge difference to scores in Unigine Heaven benchmark 4.0 
Mac Mini (late 2012) / 2.3Ghz quad i7 / 16GB / Samsung 850Pro 256GB SSD (OS) + 1TB original HD (storage) / Intel HD 4000 1536 MB / Mac OS 10.12.6 Sierra / EIZO 27" 2560x1440 via display port