I mean something like this should be fine. https://www.amazon.com/Vertical-Cable-Management-Organizer-Server/dp/B01MXOP9XR/ref=sr_1_58?dchild=1&keywords=server+cabinet&qid=1612815997&sr=8-58
That one has room where you could install additional foam between the rack and the walls if you wanted. It also already comes with a cooling fan to draw in cool air, an AC infinity system might be overkill if you cant get the hot air out of the room. If you are just taking hot air from the rack and dumping it into the open air, dont bother with AC infinity.
I use a network Rack similar to this. I know I got mine off amazon but I cant find the exact link any more. Comes with the option to install fans with holes already cut/ holes tapped in or if you dont care, just block them up. Also has rails and racks for mounting random things like lights or a camera. I have mk3s with a small stand under it to fit in everything including the spool and holder. I think mine is an 18U but a 15U would be probably be pretty good for the mini. Worth looking into in my opinion and its definitely sturdier then anything I would have made myself. I got mine for $150 so the price was probably comparable to materials and labour for the Lack enclosures.
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