ADSB.im

Supported Single Board Computers (SBCs)
Most importantly: you need a decent power supply. No, not a USB charger. An actual power supply designed for a single board computer. For most RPi3 class boards you can get away with a 5V/2.5A powersupply. For anything more powerful I recommend a 5V/4A power supply.
Boards that are actively tested and should work:

• Raspberry Pi4 or Pi5 (the Pi5 certainly is overkill, a Pi4 with 2G RAM will do just fine)
• OrangePi Zero 3 (currently my favorite when it comes to price / performance)
• Raspberry Pi Zero 2, 3a/b (note that a Raspberry Pi Zero W will NOT work; also, we are investigating some MLAT instability with Pi3 models, so potentially not the best choice)
• Libre Computing Le Potato
• Orange Pi 3LTS (no wifi support), 4LTS, 5, and 5plus (these are all known to work, but not tested regularly)

Additionally, the software stack can be installed on any board that supports DietPi, and even on most Debian or Ubuntu Linux systems. Please note that installing the adsb.im software in a VM is known to cause MLAT issues when the USB SDR is passed through to the VM.

Supported Software Defined Radios (SDRs)

• Airspy Mini (expensive, but by far the best supported SDR for ADS-B/1090MHz)
• Rtl-Sdr.com v3 and v4 dongle
• FlightAware pro stick (includes 1090MHz filter and a low noise amplifier)
• RadarBox green stick (includes 1090MHz filter and a low noise amplifier)
• AdsbExchange blue stick (includes 1090MHz filter and a low noise amplifier)
• RadarBox red stick (includes 978MHz filter and a low noise amplifier -- for UAT978)
• Nooelec NESDR Smart
• Most other RTL2838 based USB sticks should work
• SDRplay RSP1a and RSP1b - other models might work as well

Antennas

• You'll get by far the best results with an outdoor antenna mounted as high as possible (for good visibility to the horizon)
• Matthias Wirth's wiki has a great summary of some of the antenna options

Filters and LNAs (low noise amplifiers)

• some of the recommended SDRs above already include filter and LNA
• especially when investing in the Airspy Mini and a good outdoor antenna, a filtered LNA is a very useful addition. Again, great info on Matthias' wiki

SD cards (well, technically µSD cards)

• While the software fits on an 8GB card, it's generally better to go for a larger card as that extends the useful life of the card. Flash cells have a limited amount of write cycles and a larger card will balance the writes across more cells. The software stack tries to reduce unnecessary writes, but we still see especially 8GB cards die fairly regularly.
• Ideally you want a class 10 card from a name brand. ScanDisk Ultra have been known to be reliable
• Many other brands also have decent cards - but shy away from anything where the price is too good to be true
• Personally, for most of my feeders I use 64GB SanDisk Extreme cards - others have been very happy with the SanDisk Industrial and Samsung High Endurance cards.