If you go the Pi route either the Mesa 7c80 or 7c81. May go this way for the lathe.
For "future proof" I went with a Mesa Ethernet setup using an ITX board.
I started with a 7i92 intending to use a "std BoB" but then rethought things and went with a 7i76 as well. Recently got 7i73 for a Pendant and future control panel.
ATM I have the ITX in a 1u rack enclosure, Mesa cards & related PSU's in a 2u rack enclosure and stepper drivers & 48 psu in 3u rack enclosure. Sounds a bit OTT but I can slide the Mesa unit out to work on outside of the workshop. Probably not what you would call compact. TBH I stated with the 3u enclosure about 5 or 6 years ago when I was using Mach3 and the PP with another machine....... Kind grew over the years.
If going Mesa there is an install disc for Linux Mint 19.2 ie only RT atm the moment. Will look into RTAI shortly. Take note to either use dd under Linux or win32diskImager under windows to get the image onto USB or you can just burn it to DVD.
forum.linuxcnc.org/9-installing-linuxcnc...tion?start=90#157109