The 5dB outdoor Flightaware antenna will likely improve reception from the 1/4 wave or stock SDR type antenna even if used indoors. The first step to improve coverage with any antenna is to have it placed outside and above obstacles like trees, buildings, etc.
If you need feedline (between SDR and antenna) @wiedehopf’s post above has lengths of quality LMR240 with the proper connectors already installed, I would recommend these. Always get extra length too so there is a bit of slack.
The next step to increase range is a preamplifier and filter combo at the antenna as well. A bias-T and power supply (indoors likely close to your dongle/SDR) powers the preamp. This mitigates feedline losses, interference from cell towers, and brings up weaker signals.
One step at a time though, it’s quite interesting to see the effect of improvements as you go.